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Python for Beginners - Learn Coding with Python in 1 Hour — Transcript

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0:02In this Python tutorial, you're going to
0:03learn everything you need to know to
0:05start programming in Python. If you want
0:07to learn Python programming for data
0:08science, machine learning, or web
0:10development, this Python tutorial is the
0:12perfect place to learn Python. You don't
0:14need any prior knowledge in Python or
0:16programming in general. I'm going to
0:18teach you everything from scratch. I'm
0:20Mosh Hamedani, and I've taught millions
0:22of people how to code through this
0:23channel. If you're new here, make sure
0:25to subscribe as I upload new videos
0:26every week. Now, let's jump in and get
0:28started.
0:30All right, before we get started, let me
0:31give you some ideas about what you can
0:32do with Python. That's a very common
0:34question. Python is a multi-purpose
0:36programming language, so you can use it
0:38for a variety of different tasks. You
0:40can use Python for machine learning and
0:42AI. In fact, Python is the number one
0:44language for machine learning and data
0:45science projects. Python is also very
0:47popular in web development. Using Python
0:50and a framework called Django, you can
0:52build amazing websites. Here are five
0:54websites powered with Python and Django:
0:56YouTube, Instagram, Spotify, Dropbox,
1:00and Pinterest. You can also use Python
1:02in automation. With Python, you can save
1:04your time and increase your productivity
1:06by automating repetitive tasks. So, why
1:09are you learning Python? Are you
1:10learning it for automation, for data
1:12science, or web development? Let me know
1:14in the comments section below.
1:19All right, the first thing I want you to
1:20do is to head over to python.org to
1:23download the latest version of Python.
1:26So, you go to downloads and select the
1:28latest version of Python.
1:33Here in your downloads folder, you
1:34should see this package. Simply
1:36double-click it.
1:38You're going to see this Python
1:38installer.
1:40If you're on Windows, you will see this
1:41checkbox over here, add Python to path.
1:45Make sure to check it. It's really
1:46important. Otherwise, you're not going
1:48to be able to follow this tutorial.
1:51Simply click on continue
1:52again
1:53one more time
1:55I agree with the terms
1:57and install the latest version of
1:59Python.
2:00Now, here you need to enter the username
2:02and password of your computer. So,
2:05let's do that real quick.
2:09Next, you need to install a code editor.
2:11We use a code editor to write our code
2:13and execute it. The most popular code
2:15editor for Python is PyCharm. You can
2:17get it from jetbrains.com/pycharm.
2:21So, on this page
2:23click on download.
2:26You should see two different editions.
2:27One is the professional edition, which
2:29is commercial. And we also have this
2:31community edition, which is free and
2:33open source. So, we're going to download
2:35the community edition.
2:39Now, in your downloads folder, you
2:41should have this package. Let's
2:42double-click it.
2:45If you're on Windows, you're going to
2:46see an installation wizard. So, simply
2:48click on the next button until you
2:50install PyCharm. If you're on a Mac, you
2:53need to drag this PyCharm and drop it
2:55onto the applications folder.
3:00Now
3:01let's open it.
3:03The first time you open PyCharm, you
3:04have to configure a few settings. We
3:06don't want to spend time on this. So,
3:08over here, we're going to click on skip
3:10remaining and set defaults.
3:14Now, let's create a new project.
3:16Over here, we can specify the location
3:18and the name of our Python project. So,
3:22let's append hello world to this path.
3:25This is where our Python project is
3:26going to be saved. So, let's click on
3:29create.
3:32In this window, you can see the content
3:34of our project. So, here's our hello
3:36world project. Currently, we have only
3:38one folder inside this project, that is
3:40VN, which is short for virtual
3:42environment. We'll talk about virtual
3:43environments in the future. So,
3:45currently, we don't have any Python
3:47files inside this project. A real
3:49application can consist of tens or
3:51hundreds or even thousands of Python
3:53files. So, let's right-click on the
3:55project name
3:57and go to new Python file.
4:00We're going to call this file app.
4:04Now, we can collapse this project window
4:05by clicking on this icon.
4:07So, now we have more space. Let's write
4:09our first Python code.
4:11We're going to write print, all in
4:12lowercase
4:14then add parentheses
4:15then add quotes, either single quotes or
4:18double quotes.
4:20And inside these quotes, we're going to
4:21write hello world.
4:23So, this is what we call a string. A
4:25string means a string or sequence of
4:28characters. In simple words, that means
4:30textual data. So, in Python and in many
4:33other programming languages, whenever
4:35we're dealing with textual data, we
4:37should always surround our text with
4:39quotes.
4:40In Python, we can use single or double
4:42quotes.
4:44Now, this print you see here is a
4:45function built into Python, and we can
4:48use it to print a message on our
4:49application window.
4:51So, let me show you how to run this
4:52code.
4:54On the top we go to the run menu and
4:56then select run. Note that there is a
4:59shortcut associated with this command. I
5:01always use shortcuts because they
5:02increase my productivity. So,
5:05let's click on this. Now, select app
5:09and over here
5:10you can see this little window. This is
5:12what we call the terminal window, and it
5:14shows the output of our program.
5:16So, here's the hello world message
5:18printed in the terminal window. Now, as
5:20you learn more Python, you will learn
5:22how to build applications that have a
5:23graphical user interface. That's an
5:25advanced topic, so for now, let's not
5:27worry about it.
5:34All right, now let's talk about
5:35variables. We use variables to
5:37temporarily store data in a computer's
5:40memory. For example, we can store the
5:42price of a product or someone's name,
5:44their email, their age, and so on. Let
5:47me show you. So,
5:48to declare a variable, we start by
5:50typing a name for that variable. Let's
5:52say age.
5:54Then we add an equal sign
5:56and then we type a value. Let's say 20.
5:59So, with this, we're storing the number
6:0020 somewhere in our computer's memory
6:03and we're attaching this age as a label
6:05for that memory location. So, now we can
6:08read the value at this memory location
6:10and print it on the terminal. So,
6:12instead of printing hello world, we want
6:14to print the value of the age variable.
6:17So, I'm going to delete what we have
6:19inside parentheses
6:21and type age. Note that I'm not adding
6:25quotes because if I run this program,
6:27we'll see the text age on the terminal.
6:29We don't want that. We want the value of
6:31the age variable. So,
6:34let's remove the quotes
6:35and print the value of the age variable.
6:38Now, here on the toolbar, you can click
6:41on this play icon to run your program,
6:43or you can use the shortcut that I
6:44showed you in the last video. So, the
6:47shortcut is over here. On a Mac, that's
6:49control, shift, and R.
6:52So,
6:53there you go.
6:55Now, you can see the value of the age
6:56variable.
6:58Now, we can also change the value of a
6:59variable. For example, on line two
7:02we can set age to 30.
7:05Now, when we run our program
7:07we see 30. So, as you can see, our
7:09program gets executed from top to
7:11bottom.
7:13So, this is how we can declare and use a
7:14variable. Now, let's look at a few more
7:16examples.
7:17So, I'm going to declare another
7:19variable called price and set it to
7:2219.95.
7:25So, in Python, we can use numbers with a
7:26decimal point or whole numbers.
7:30We can also declare a variable and
7:32assign it a string value. So, let's say
7:35first_name.
7:38So, if you want to use multiple words in
7:40the name of a variable, we should
7:41separate them using an underscore. This
7:44makes our code more readable. See what
7:46would happen if I didn't use this
7:48underline.
7:50This is not easily readable. So, we
7:52always separate multiple words by an
7:54underscore.
7:56Now, we set this to a string. So, we can
7:58use single quotes or
8:00double quotes.
8:01Let's say Mosh.
8:02We also have a special type of value
8:04called a boolean value, which can be
8:06true or false. That is like yes or no in
8:09English. Let me show you. So,
8:12I'm going to declare another variable
8:14called is_online
8:16and set it to true.
8:18We could also set it to false. What we
8:21have here is called a boolean value.
8:23Now, note that Python is a
8:25case-sensitive language, so it's
8:27sensitive to lowercase and uppercase
8:29letters. In this case, if I use a
8:31lowercase f
8:34we can see an error over here because
8:35this is not recognized in Python.
8:38So, false with a capital F is a special
8:40keyword in Python that represents the
8:43boolean false value.
8:45So, this is how we can declare and use
8:47variables in Python.
8:48All right, now here's a little exercise
8:50for you. Imagine you want to write a
8:52program for a hospital. So, we're going
8:54to check in a patient named John Smith.
8:56He's 20 years old and is a new patient.
8:59I want you to declare a few variables to
9:01store these values. Use the comment box
9:03below to share your code with others.
9:12In this tutorial, I'm going to show you
9:13how to receive input from the user.
9:16So, in Python, we have another built-in
9:18function called input. We use this to
9:20read a value from the terminal window.
9:22Let me show you. So,
9:24we add parentheses
9:26then we type a string. Here, we can type
9:28a message like what is your name? We add
9:31a question mark followed by a space.
9:34You'll see why we need this space in a
9:35second. So, let's run this program.
9:39We get this message. Now, we have to
9:41enter a value. So, we click over here.
9:44Now, you can see that the carrot is
9:45separated from the question mark. This
9:47is because of the white space that we
9:49added over here.
9:51So, now we have to type a value. Let's
9:53say John. When we press enter
9:56this function will return the value that
9:58we entered in the terminal window. So,
10:01we can get that value and store it in a
10:02variable.
10:04So, let's declare a variable called name
10:06and set it to the return value of the
10:09input function.
10:10Now, we can print a greeting message for
10:12this user. So,
10:14we use the print function.
10:16We say, "Hello."
10:18We add a space.
10:20Now, after this string, we want to add
10:22the value of the name variable. So, we
10:24use the plus sign and then type name.
10:27What we're doing here is called string
10:30concatenation. So, we're combining this
10:32string with another string.
10:35Now, let's run our program and see what
10:36happens. So, what is your name? Mosh.
10:40Now,
10:41we get this message, "Hello Mosh."
10:43So, this is how we can use the input
10:44function in Python.
10:52You'll learn about the three types of
10:53data in Python. We have numbers,
10:56strings, and booleans.
10:59Now, there are times you want to convert
11:00the value of a variable from one type to
11:02another. Let me show you. So, we're
11:05going to use our input function
11:07to read the user's birth year. So,
11:10"Enter your birth year."
11:13Now, this input function is going to
11:15return a value, so we can store it in a
11:17variable called
11:19birth_year.
11:21Okay?
11:22Now, let's write code to calculate the
11:24age of this user. So, we write an
11:26expression like this. Currently, we are
11:28in the year 2020. So, 2020 minus
11:32birth year.
11:34This expression or piece of code is
11:35going to produce a value. So, once
11:37again, we can store that value in a
11:39variable. Let's call that variable age.
11:43Now, let's print age
11:45on the terminal.
11:46Let's run our program and see what
11:47happens.
11:49So, my birth year is 1982.
11:52Enter. Oops, our program crashed. So,
11:55whenever you see this red message, that
11:57indicates an error.
11:59So, this error occurred in this file,
12:02that is our app.py, on line two.
12:05Right below that, you can see the piece
12:07of code that generated this error.
12:09So, that is this expression, 2020 minus
12:12birth year. Now, below that, you can see
12:14the type of error. So, here we have
12:17unsupported types for subtraction.
12:21We have int and str.
12:24What are these? Well, this int is short
12:26for integer, and that represents a whole
12:28number in programming. So,
12:312020 is an example of an integer.
12:34Now, birth year
12:36is an example of a string because
12:38whenever we call the input function,
12:40this function will return a value as a
12:42string, even if we enter a number. In
12:45other words, when I entered 1982, this
12:48input function returned a string with
12:50these characters, 1982. So, this string
12:53is different from the number 1982.
12:57They're completely different types. So,
12:59in this case,
13:00let me delete these lines.
13:02The reason we got this error is that we
13:04tried to subtract a string from an
13:07integer. So, our code looked like this,
13:101982.
13:12Now, Python doesn't know how to subtract
13:14a string from an integer.
13:16So, to solve this problem,
13:18we need to convert this string to an
13:19integer.
13:21Now, in Python, we have a bunch of
13:22built-in functions for converting the
13:24types of our variables. So, we have this
13:27int function.
13:29We can pass our birth year to it,
13:31and this will return the numeric
13:33representation of the birth year. So, to
13:36solve this problem,
13:38we need to replace
13:40the string
13:42with the int function.
13:43So, let's see what's going on here.
13:45On the first line, we call the input
13:47function. This returns a string.
13:49On the second line, we pass the string
13:52to our int function. The int function
13:54will return the numeric representation
13:56of the birth year.
13:58Then,
13:59we subtract it from 2020, we get the
14:01age, and store it in the age variable.
14:04Now, let's run our program.
14:06So, 1982,
14:08and there you go. I'm 38 years old.
14:11So, this is how the int function works.
14:14Now, we also have another built-in
14:16function called float. That is for
14:18converting a value to a floating-point
14:20number.
14:21A floating-point number in Python and
14:23other programming languages is a number
14:25with a decimal point. So, 10 is an
14:29integer, and 10.1 is a float.
14:32So, we have int, we have float, and we
14:35also have bool
14:36for converting a value to a boolean.
14:39And finally, we have str
14:41for converting a value to a string.
14:44So, these are the built-in functions for
14:46converting the type of our variables.
14:48Now, here's a little exercise for you. I
14:50want you to write a basic calculator
14:52program.
14:53So, here we have to enter two numbers.
14:55You can type a whole number or a number
14:57with a decimal point.
15:00And then our program will print the sum
15:02of these two numbers.
15:03So, pause the video, spend two minutes
15:05on this exercise, and then see my
15:07solution.
15:11All right, first we're going to call our
15:12input function to read the first number.
15:15We get the result and store it in a
15:16variable called first.
15:19Now, let's declare
15:21another variable called second and read
15:24the second number.
15:26Now,
15:27we calculate the sum.
15:29So, that is first plus second.
15:32Now, let's see what happens when we
15:33print sum on the terminal.
15:36So, I enter 10 and 20,
15:39but instead of 30, we get 1020. This is
15:42because we're combining or concatenating
15:44two strings. So,
15:47as I told you before, the input function
15:49returns a string. So,
15:52this line will be equivalent to first
15:55equals 10.
15:56We're dealing with a string, not an
15:58integer.
15:59Similarly,
16:00second is going to be
16:0220 as a string. So, when we combine two
16:05strings, 10 plus 20, we'll get 1020
16:10because we're dealing with textual data,
16:12okay? So, to solve this problem,
16:16we need to convert the values we read to
16:18their numeric representation. So, over
16:20here,
16:23we're going to pass first to our int
16:25function,
16:27and here as well.
16:28Now, let's run our program.
16:30So, we enter 10 and 20, we get 30.
16:34What if we enter a floating-point
16:35number? So, 10.1 and 20.
16:40We got an error.
16:41So, to solve this problem,
16:44we need to treat both these values as
16:46floats. So, instead of the int function,
16:49we're going to use the float function.
16:52Now, let's run our program one more
16:54time.
16:55We enter a whole number and a
16:57floating-point number.
16:59So, the result is correct.
17:01Now, let's add a label over here. So,
17:04sum
17:05is
17:07plus sum.
17:08Let's run our program
17:10one more time. 10 and 20.
17:12Once again, we got an error. The error
17:14is saying that Python can only
17:16concatenate strings, not floats to
17:18strings.
17:21So, on line four, we have a string.
17:23We're concatenating this with a float
17:26because the result of this expression is
17:28a floating-point number. We're adding
17:30two floats, so the result is a float as
17:32well. So, Python doesn't know how to
17:35evaluate code like this.
17:38It doesn't know how to concatenate a
17:40float
17:42to a string. To solve this problem,
17:45we need to convert sum to a string. So,
17:47this is where
17:48we use the str function.
17:51Now, let's run the program again. So, 10
17:54plus 20.1, and here's the result.
17:58And one last thing.
17:59In this example, I'm calling the float
18:01function at the time we want to
18:03calculate the sum of these two numbers,
18:05but this is not a requirement. You can
18:07call the float function
18:09over here. So, this input function
18:11returns a string. We can pass that
18:14string to our float function. Take a
18:16look. So, float parentheses like this.
18:20So, the value that we're passing to the
18:22float function is the value that is
18:24returned from the input function.
18:26Similarly,
18:29we call the float function over here.
18:32Now,
18:33we can change this expression to first
18:35plus second.
18:37That is another way to write this piece
18:39of code.
18:40So, type conversion is important in
18:41Python and other programming languages.
18:44There are times you need to convert the
18:45type of a variable to a different type.
18:54In this tutorial, I'm going to show you
18:55a bunch of cool things you can do with
18:56strings in Python.
18:58So, let's start by declaring a variable
19:00called course
19:01and set it to Python for
19:04beginners.
19:06Now, this string that we have over here
19:07is technically an object. An object in
19:10Python is like an object in the real
19:12world. As a metaphor, think of the
19:14remote control of your TV.
19:16This remote control is an object, and it
19:18has a bunch of capabilities. It has a
19:19bunch of buttons for turning your TV on,
19:22turning it off, changing the volume, and
19:24so on.
19:24Now, in this program, this course
19:26variable is storing a string object.
19:29This string object has a bunch of
19:30capabilities. So, if you type course.
19:33dot, you can see all the capabilities
19:36available in a string object. These are
19:38basically functions that you can call,
19:40just like the print or input functions.
19:42The difference is that the print and
19:44input functions are general-purpose
19:46functions. They don't belong to a
19:47particular object, but the functions you
19:50see over here are specific to a string.
19:52Now more accurately, we refer to these
19:54as methods. So when a function is part
19:57of an object, we refer to that function
19:59as a method. So,
20:01let's look at a few examples. Here we
20:03have a function or a method called upper
20:06and we use that to convert a string to
20:07upper case.
20:09So if we print
20:10course.upper
20:12and run this program, you can see our
20:14course in upper case. Pretty useful.
20:17Now what you need to understand here is
20:19that this upper method does not change
20:21our original string. It will return a
20:23new string. So right after this, if we
20:26print course,
20:29you can see that our course variable is
20:31not affected. So the upper method
20:33returns a new string.
20:36Now similarly, we have another method
20:38called lower for converting a string to
20:40lower case.
20:41We have a method called find to see if
20:44our string contains a character or a
20:46sequence of characters.
20:47For example, here we can pass Y and this
20:51will return the index of the first
20:53occurrence of Y in our string. So,
20:57in Python, the index of the first
20:59character in a string is zero. So here
21:01we have 0 1 2 3 4 and so on.
21:04So when we run this program, you're
21:05going to see one on the terminal because
21:07the index of Y is one. Take a look.
21:11First I'm going to delete this line. We
21:12don't need it anymore. Also, let's
21:14delete this line.
21:16Let's run the program. There you go.
21:20Now as I told you before, Python is
21:21sensitive to lower case and upper case
21:24letters. So if I pass an upper case Y
21:27here,
21:28this find method returns -1 because we
21:31don't have an upper case Y in this
21:33string.
21:34We can also pass a sequence of
21:35characters. For example, four.
21:38So this will return the index of the
21:39word four. Take a look.
21:43So it's seven.
21:45Now there are times we want to replace
21:46something in a string with something
21:47else.
21:48To do that, we use the replace method.
21:51Replace.
21:52So we can replace four with a string
21:56containing the number four. Take a look.
21:59So Python for beginners.
22:02Obviously,
22:03if you look for a character or a
22:04sequence of characters that don't exist
22:06in our string, nothing is going to
22:08happen. For example, if you try to
22:10replace X with four, obviously, we don't
22:13have X here, so nothing is going to
22:15happen.
22:16Also, just like the upper method, the
22:19replace method is not going to modify
22:21our original string. So it's going to
22:23return a new string. This is because
22:25strings in Python and many other
22:27programming languages are immutable. We
22:29cannot change them once we create them.
22:32Whenever we want to change a string,
22:33we'll end up with a new string object in
22:35memory.
22:36Now one last thing I want to cover in
22:37this tutorial. There are times you want
22:39to see if your string contains a
22:41character or a sequence of characters.
22:43One way to do that is using the find
22:45method that we talked about. So let's
22:48see if our string contains Python.
22:52Now when we run this program,
22:54that is the index of the first
22:56occurrence of the word Python in our
22:58string.
22:59Now in Python, we can also use the in
23:01operator.
23:02So we can write an expression like this.
23:05We type a string,
23:07Python,
23:08then we type in. This is a special
23:10keyword in Python. This is what we call
23:13the in operator.
23:15So after that,
23:16we type the name of our variable.
23:18So with this expression, we're checking
23:20to see if we have Python in course. As
23:23you can see, Python code is very
23:25readable. It's like plain English. So
23:27when we run this program,
23:29instead of seeing the index of the first
23:31occurrence of Python, we see a boolean
23:34value. This is more desirable in a lot
23:36of cases.
23:37Next we're going to look at arithmetic
23:38operations.
23:46In this tutorial, I'm going to show you
23:47the arithmetic operators that we have in
23:49Python. These are the same arithmetic
23:51operators that we have in math. For
23:53example, we can add numbers, we can
23:55subtract them, multiply them and so on.
23:57So let's print 10 + 3.
24:01When we run this program, we get 13.
24:03So this is the addition operator. We
24:06also have subtraction.
24:07We have multiplication
24:09and division. Now technically, we have
24:12two different types of division
24:13operators. We have a division with one
24:15slash and another with two slashes.
24:18Let's look at the differences. If you
24:20use a single slash,
24:22we get a floating point number that is a
24:24number with a decimal point. But if you
24:26use double slashes,
24:28we get
24:29an integer, a whole number.
24:32We also have the modulus operator that
24:34is indicated by a percent sign and this
24:37returns the remainder of the division of
24:3910 by 3. So that is one.
24:43And finally, we have the exponent
24:44operator that is indicated by two
24:46asterisks. So this is 10 to the power of
24:50three. So when we run this, we get
24:521,000.
24:54Now,
24:54for all these operators that you saw, we
24:56have an augmented assignment operator.
24:59Let me explain what it means. So let's
25:01say we have a variable called X
25:03and we set it to 10.
25:05Now we want to increment the value of X
25:07by three. So we have to write code like
25:09this. X
25:10= X + 3. When Python executes this code,
25:14it's going to evaluate this expression
25:16or this piece of code. The result of
25:18this expression is 10 + 3 which is 13.
25:21Then it will store 13 in the X.
25:24Now there is another way to achieve the
25:26same result using less code.
25:28We can type X + = 3.
25:32What we have on line three is exactly
25:34identical to what we have on line two.
25:36So what we have here is called the
25:38augmented assignment operator. So we
25:41have this assignment operator, but we
25:43have augmented or enhanced it.
25:46Now here we can also use
25:48subtraction to decrease the value of X
25:50by three. We can use multiplication and
25:53so on.
25:54So these are the arithmetic operators in
25:56Python.
26:03All right, let me ask you a question.
26:04I'm going to declare a variable called X
26:07and set it to 10 + 3 * 2.
26:10What do you think is the result of this
26:11expression? This is a basic math
26:13question that unfortunately, a lot of
26:15people fail to answer.
26:17The answer is 16.
26:19Here's the reason.
26:20In math, we have this concept called
26:22operator precedence and that determines
26:24the order in which these operators are
26:26applied. So multiplication and division
26:30have a higher order. So this part of the
26:32expression gets evaluated first. So 2 *
26:343 is 6 and then the result is added to
26:3810. That is why the result of this
26:40expression is 16.
26:42Now in Python, operator precedence is
26:44exactly like math, but we can always
26:46change it using parentheses. For
26:48example, in this expression, if you want
26:5010 + 3 to be evaluated first, we can
26:53wrap it in parentheses.
26:55So,
26:56like this.
26:57Now when we execute this code, we're
26:59going to see 26 because 10 + 3 is 13 and
27:03that divided by 2 is 26. Let's verify
27:05this. So print X
27:08and we get 26.
27:15So you learned about the arithmetic
27:17operators in Python. Now in Python, we
27:19have another set of operators called
27:21comparison operators. We use these
27:23operators to compare values. Let me show
27:26you. So I'm going to declare a variable
27:28called X
27:29and set it to an expression like this. 3
27:32is greater than 2. So what we have here,
27:35this piece of code, this expression is
27:37called a boolean expression because it
27:39produces a boolean value.
27:41So in this case, because 3 is greater
27:43than 2, the result of this expression is
27:46the boolean true.
27:47So if we print X,
27:51we get true on the terminal.
27:53So here is the greater than operator. We
27:55also have greater than or equal to. We
27:58have less than. We have less than or
28:01equal to.
28:02Here's the equality operator which is
28:04indicated by two equal signs. Do not
28:07confuse this with the assignment
28:08operator. So here we're comparing three
28:11and two for equality. So if we run our
28:13program,
28:15we see false because three does not
28:17equal to two.
28:19So here's the equality operator. We also
28:21have
28:22the not equality operator that is
28:24indicated by an exclamation mark
28:26followed by an equal sign.
28:29So let's quickly recap.
28:31Here are the comparison operators we
28:32have in Python.
28:34Greater than, greater than or equal to,
28:36less than, less than or equal to,
28:39equal and not equal.
28:41These operators are extremely important
28:43in real Python programs because quite
28:45often we have to compare values to
28:47evaluate certain conditions. You're
28:49going to see that soon.
28:56In Python, we have another set of
28:58operators called logical operators.
29:00We use these operators to build complex
29:02rules and conditions. Let me show you.
29:05So I'm going to declare a variable
29:06called price and set it to 25.
29:09Now let's print
29:10a boolean expression like this.
29:12Price is greater than 10.
29:15Now let's say we want to check to see if
29:17the price is between 10 and 30.
29:20This is where we use the logical and
29:22operator. So we type and and right after
29:25that, we type another boolean
29:27expression. So price less than 30.
29:31So with this and operator, if both these
29:33boolean expressions return true, the
29:36result of this entire expression will be
29:37true. Take a look. So,
29:41in this case we get true
29:43because the price is between 10 and $30.
29:46We also have
29:48the or operator. With the or operator,
29:51if at least one of these boolean
29:52expressions returns true, then the
29:55result of this entire expression will be
29:56true.
29:57To demonstrate this, I'm going to change
29:59price to five. Let's see how Python is
30:02going to execute this code. So, first
30:04it's going to look at this boolean
30:05expression. Is price greater than 10?
30:08No, it's not. So, it will keep going.
30:11Then it will look at the second boolean
30:13expression. Is price less than 30? It
30:16sure is. So, the result of this entire
30:18expression will be true. Take a look.
30:22There you go.
30:23We also have the not operator, which
30:25basically inverses any values that you
30:27give it. Let me show you. So,
30:30we're going to have one boolean
30:32expression, price greater than 10.
30:34The result of this expression is false.
30:37Now, if you apply the not operator, this
30:40will inverse false to true. So, let me
30:43run the program, we get true.
30:46So, let's quickly recap. In Python, we
30:48have three logical operators. We have
30:50logical and, which returns true if both
30:53expressions return true.
30:55We have logical or, which returns true
30:57if at least one expression returns true.
31:00And we have not, which inverses any
31:02value that we give it.
31:10In this tutorial, we're going to talk
31:11about if statements in Python. We use if
31:14statements to make decisions in our
31:15programs. For example, we can declare a
31:18variable called temperature, and
31:19depending on the value of this variable,
31:21we can print different messages on the
31:23terminal. Let me show you.
31:25So, here's our temperature variable.
31:27We set it to 35.
31:29Now, let's say if temperature is greater
31:32than 30, we want to print a message
31:34saying it's a hot day.
31:35So, we type if,
31:37then we type a condition, and this is
31:39where we use our comparison operators.
31:42So, we type temperature greater than 30.
31:46Then, so we add a colon, and see what
31:49happens when I press enter now.
31:51The caret is indented, and this
31:53represents a block of code. So, the code
31:56that we write over here will be executed
31:58if this condition is true. Otherwise,
32:00it's not going to be executed. Let me
32:02show you. So,
32:04we're going to print
32:06it's a hot day.
32:08And by the way, note that here I've
32:09surrounded the string with double
32:11quotes, because here we have a single
32:14quote as an apostrophe. So, I couldn't
32:17declare a string like this with single
32:19quotes. If I typed it's a hot day, look,
32:23Python gets confused. Because it thinks
32:26the single quote represents the end of
32:28our string, so it doesn't recognize the
32:30subsequent characters, okay? So, that's
32:32why we use
32:34double quotes here,
32:36so we can have an apostrophe in our
32:38string.
32:39So, it's a hot day.
32:41Now, if I press enter again,
32:43the caret is indented, so the code that
32:46we write here will be part of our if
32:48block, and it will get executed if this
32:50condition is true. So, here we can print
32:53a second message, drink plenty of water.
32:57Now, to terminate this block, we press
32:59enter, and then press shift and tab.
33:02The caret is no longer indented, so the
33:05code that we write here will always get
33:07executed, no matter what, whether this
33:09condition is true or not.
33:11Now, in C-based programming languages
33:13like C++, C#, Java, and JavaScript, we
33:17represent a block of code using curly
33:19braces. So,
33:21you start a block of code using a left
33:23brace, and then end it using a right
33:26brace. In Python, we don't have curly
33:28braces. So, we use indentation to
33:30represent a block of code, okay?
33:33So, in this case,
33:35these two lines are indented, and that
33:37means they are part of this block of
33:40code.
33:41Now, let's run the program and see what
33:42happens.
33:44So, we see these two messages because
33:46the temperature is greater than 30.
33:48Now,
33:49if I change the temperature to 25,
33:52and run the program again, we don't see
33:54anything, okay?
33:57Now, after this block, let's print done.
34:01Because this code is not indented, it
34:03will always get executed. It's not part
34:05of our if block, okay? So, take a look.
34:09Here's the done message.
34:11Now, let's add a second condition.
34:14So, if temperature is not greater than
34:1630, that means it's less than or equal
34:18to 30.
34:20So, I'm going to add a second condition.
34:23So, if the temperature is between 20 and
34:2530, I want to print it's a nice day.
34:28So, here we type L if, that is short for
34:31else if.
34:33And here we type a second condition.
34:35So, temperature greater than 20.
34:39We add a colon, press enter. Now, we
34:42have a new block.
34:43So, here we can print
34:45it's a nice day.
34:48So, if this condition is true, that
34:50means the temperature
34:52is greater than 20, and less than or
34:54equal to 30.
34:56Now, what we have here is called a
34:57comment. That is why it's grayed out.
35:00It's not real code, it's just some note
35:02that we add to our program. Python is
35:04not going to execute this. So, whenever
35:06we type a pound sign, what we have after
35:08is treated as a comment, okay?
35:11So, if this condition is true, then
35:13we're going to see this message on the
35:15terminal. Let's run our program and
35:17verify this.
35:19There you go. The temperature is 25,
35:21that's why we see this message.
35:23Now, we can have as many conditions as
35:25we want. There are no limitations, okay?
35:28So, let's add another condition. L if,
35:31temperature is greater than 10, then
35:35we're going to print
35:37it's a bit cold.
35:39Now, in this case, if this condition is
35:41true, that means the temperature is
35:43greater than 10,
35:45and less than or equal to 20.
35:48Now, finally, if the temperature is less
35:49than 10, let's print a message saying
35:51it's a cold day. So,
35:54here we type else, then we add a colon,
35:57and now we have a new block. So, this
36:00code will get executed if none of the
36:02above conditions are true. So, here we
36:05can print
36:07it's cold.
36:10So, this is how we use if statements to
36:12make decisions in our programs.
36:20Here's a great exercise for you to
36:21practice what you have learned so far. I
36:23want you to write a weight converter
36:25program like this.
36:27So, this program is asking me my weight.
36:29I enter 170.
36:31Next, it's asking me if the weight is in
36:34kilograms or pounds. So, I can type K
36:36for kilograms, or L for pounds. I can
36:39type a lowercase L, or an uppercase L.
36:42It doesn't matter. So, let's go with a
36:44lowercase L.
36:46Now, it tells me weight in kilogram is
36:4976.5.
36:51So, go ahead and spend 5 minutes on this
36:52exercise. You can use the comment box
36:54below to show your code with others. And
36:57then when you're done, come back and see
36:58my solution.
37:02So, first we call our input function to
37:05ask the first question. Weight.
37:08We get the result and store it in a
37:09variable called weight.
37:12Next, we call the input function one
37:13more time to ask the second question.
37:16Is this in kilogram
37:18or
37:19pounds?
37:22We get the result and store it in a
37:24variable called unit.
37:25This is where we're going to use an if
37:27statement.
37:28So,
37:29we want to check to see if unit equals
37:32K.
37:34Then, we should convert the weight to
37:36pounds and print it on the terminal.
37:38However,
37:39with this code, if I type a lowercase K,
37:41this condition is not going to be true,
37:43because earlier I told you that Python
37:45is a case-sensitive language. So,
37:48we need to convert this string to
37:50uppercase. Earlier we talked about
37:52string methods. So, if you type dot, we
37:54can see all the functions or methods
37:56available in a string object. So, we use
37:59the upper method,
38:01and this returns a new string in
38:02uppercase.
38:04Now, if this condition is true, first we
38:06need to convert the weight to pounds.
38:08So, we declare a new variable called
38:10converted,
38:12get the weight, and divide it by 0.45.
38:17And then we can print this on the
38:18terminal. So,
38:21we say weight
38:22in pounds is
38:24then we append converted.
38:27Now, to terminate this block, we press
38:29shift and tab.
38:31Else, colon.
38:33So, if this condition is not true, that
38:35means the weight was entered in pounds,
38:37so we need to convert it to kilograms.
38:39Once again, we declare a variable
38:41converted, and set it to weight times
38:450.45.
38:47And then we print weight in kilograms,
38:52and here we concatenate
38:54the string with converted.
38:56All right. Now, we need to terminate
38:58this block, so we press enter, then
39:00shift and tab. Good.
39:02Now, if you run this program, we're
39:03going to see an error. Let me show you.
39:05So, let's run it.
39:07Here I'm going to enter 170.
39:10Then I type a lowercase L. Okay. Here's
39:14an error.
39:15Can't multiply sequence by non-int of
39:17type float. So, this is where we got
39:20this error. When we tried to multiply
39:23the weight by 0.45.
39:26So,
39:27that is line seven in our code. Now, the
39:29reason this is happening is because the
39:31weight variable is storing a string
39:33object. Because earlier I told you the
39:36input function always returns a string.
39:39So, here we need to convert the weight
39:41to a number.
39:42We can either use the int or the float
39:45function.
39:46Let's run the program one more time.
39:48So,
39:49170
39:52in pounds.
39:53Here's the second error. Can only
39:55concatenate string, not float to string.
39:59And that error occurred
40:01over here.
40:02When we try to print the weight in
40:04kilograms. So,
40:06look at line seven.
40:08In this case, weight is an integer.
40:10We're multiplying an integer by a float,
40:12and the result of this operation is
40:14going to be a float.
40:16Now, on line eight, we're trying to
40:18concatenate or combine a string with a
40:21float, and Python doesn't know how to
40:23execute this code. To solve this
40:25problem, we need to convert this float
40:27to a string. So, here we use the
40:29built-in str function.
40:32Let's run the program and see what
40:33happens.
40:34So,
40:35170
40:37in pounds, and here's my weight in
40:40kilograms. Now, let's try entering a
40:42weight in kilograms. So, running one
40:44more time.
40:45Let's say 76
40:47kilos.
40:49Here we get a familiar error. Can only
40:52concatenate string to string, not float.
40:55So, this error occurred
40:56on line five, where we try to
40:58concatenate a string
41:01to a float. So, once again, we need to
41:03convert this to a string object.
41:06Now, let's run the program one more
41:07time.
41:0976
41:10kilos
41:11is equal to 168 lbs.
41:16Hey guys, I just wanted to let you know
41:17that I have an online coding school at
41:19codewithmosh.com, where you can find
41:21plenty of courses on web and mobile
41:22development. In fact, I have a
41:24comprehensive Python course that teaches
41:26you everything about Python from the
41:28basics to more advanced concepts. So,
41:30after you watch this tutorial, if you
41:32want to learn more, you may want to look
41:33at my Python course. It comes with a
41:3530-day money-back guarantee and a
41:36certificate of completion you can add to
41:38your resume. In case you're interested,
41:40the link is below this video.
41:46In this tutorial, we're going to talk
41:47about while loops in Python. We use
41:50while loops to repeat a block of code
41:52multiple times. For example, let's say
41:54you want to print the numbers one to
41:55five.
41:56A poor way of doing this is writing code
41:58like this. Print one, then print two,
42:01print three,
42:02print four, and print five.
42:05Now, why is this a bad approach? Well,
42:07what if you wanted to print the numbers
42:09one to 1 million? We don't want to write
42:111 million lines of code, each line
42:13printing a number. This is where you use
42:15while loops. So,
42:17we start off by declaring a variable
42:19like I, and set it to our initial
42:21number. Let's say one.
42:23Then we type while, and here we type a
42:25condition. So, once again, we can use
42:27our comparison operators.
42:29Let's say I less than five. Less than or
42:32equal to five.
42:34As long as this condition is true, then
42:36the code that we write inside of the
42:38while block will get executed. So, here
42:40we type a colon and press enter. Now, we
42:43have a block of code.
42:45In this block, we can print I,
42:48and then we need to increment I by one.
42:50So, we set I to I + 1. If we don't do
42:53this, I will always be one, and this
42:56block of code
42:57will get executed indefinitely. It will
43:00never terminate. Basically, our program
43:02will continue running until it runs out
43:04of memory.
43:05So, in the first iteration, I is one, is
43:08less than five, so Python is going to
43:10execute this block of code. It will
43:13print one on the terminal, and then I
43:15becomes two.
43:16Then the control moves back over here.
43:18So, Python evaluates this condition. Two
43:21is less than or equal to five, so the
43:23condition is true, and once again,
43:25Python is going to execute this block
43:27one more time.
43:28In the second iteration, we're going to
43:30see two on the terminal, and then I will
43:32become three.
43:33So, this will continue until this
43:35condition is no longer true. Let me show
43:37you. So,
43:39let's run this program.
43:41Now, we see the numbers one to five. So,
43:43this is the beauty of while loops.
43:45I can easily change five
43:48to 1
43:49thousand. And by the way, I'm separating
43:51these three digits using an underscore.
43:53This makes my number more readable. We
43:55don't have to add this, but it just
43:56makes our code more readable.
43:58So, let's run the program.
44:01Now, we see the numbers one to 1
44:02thousand. It's much easier than 1
44:05thousand lines of code, each printing a
44:07number. Okay?
44:08Now, let me show you something really
44:09cool.
44:10So, I'm going to change this
44:12to 10.
44:14Now, instead of printing I, I want to
44:17print an expression. So, I'm going to
44:19multiply I
44:21by a string,
44:22an asterisk.
44:23Now, you might be confused here, because
44:25earlier I told you that in Python, we
44:27cannot concatenate a number to a string.
44:30But here I'm using the multiplication
44:32operator. Well, this is different. We
44:34can multiply a number by a string, and
44:37this will repeat that string based on
44:39the value of that number. So, if I is
44:42one, we're going to see one asterisk. If
44:45I is five, we're going to see five
44:46asterisks. Let me show you. So, when we
44:49run this program,
44:51we see this triangle shape, because in
44:53the first iteration, I is one, so we see
44:56one asterisk. In every iteration, I is
44:59incremented by one, so we see one extra
45:02asterisk. And finally, in the last
45:04iteration, I is 10, and we see 10
45:07asterisks on the terminal.
45:15So, you have learned about three types
45:16of data in Python.
45:18We have numbers, which can be integers
45:20or floats. We have booleans and strings.
45:24These are what they refer to as
45:26primitive or basic types in Python.
45:29Now, in Python, we have a bunch of
45:30complex types as well. These complex
45:32types are very useful in building real
45:34applications.
45:36In this tutorial, we're going to talk
45:37about lists. We use lists whenever we
45:40want to represent a list of objects,
45:42like a list of numbers or a list of
45:44names. Let me show you.
45:45So, I'm going to declare a variable
45:47called names,
45:49and set it to a list of names.
45:51So, here we add square brackets to
45:53represent a list.
45:54And now we can add one or more objects
45:56inside this list. In this list, we add a
45:58bunch of names,
46:00like John,
46:01Bob,
46:03Mosh,
46:04Sam, and Mary.
46:06So, we separate these elements, these
46:08items, using a comma. Okay?
46:10Now,
46:11let's print our list. So, print names.
46:15Take a look.
46:16It comes out exactly like how we wrote
46:18it.
46:19Now, we can also get individual elements
46:21in this list. For example, if you want
46:23to get the first element in this list,
46:26here we type a pair of square brackets,
46:28and inside the square brackets, we type
46:30an index.
46:32The index of the first element in this
46:33list is zero. So, now, when we run this
46:36program, we're going to see John on the
46:38terminal.
46:39There you go.
46:40Now, in Python, we can also use a
46:43negative index. This is a feature that I
46:45personally have not seen in other
46:47programming languages.
46:48So, if zero represents the first element
46:52in this list, what do you think negative
46:54one represents?
46:56It represents the last element in this
46:58list. Let's verify it. So, let's run the
47:01program, and here's Mary.
47:03What about
47:06negative two? Well, that represents the
47:09second element
47:10from the end of the list.
47:12So, let's run the program, and here's
47:14Sam.
47:15Now, we can also change an object at a
47:17given index. For example, let's say here
47:20we made a mistake, and this John should
47:22not be spelled with an H. So, we need to
47:25reset it. We type names of zero.
47:29Now, we treat this like a regular
47:30variable. So, we set it to a new value.
47:33We set it to John without an H. Now,
47:36let's print our list.
47:38And here's our updated list. Beautiful.
47:41We can also select a range of values.
47:44For example, let's say we're only
47:45interested in the first three names.
47:49So, over here, we type square brackets,
47:51and here we need to type two indexes, a
47:54start index and an end index.
47:56Our start index is zero, because we want
47:58to start from here,
48:00and our end index is going to be zero,
48:03one, two, plus one, that's going to be
48:06three. So, we add a colon, three.
48:10So, Python is going to return all the
48:11elements from the start index up to the
48:14end index, but excluding the end index.
48:17So, it's going to return the elements at
48:19index zero, one, and two. Take a look.
48:24Here are the first three names.
48:27And by the way,
48:29this expression does not modify our
48:31original list. It returns a new list.
48:34So, right after this print statement, if
48:37we print our original list,
48:40we can see that it's not changed.
48:42So, this is how we use lists in Python.
48:51Earlier, I told you that strings in
48:52Python are objects. Objects in
48:55programming are kind of like objects in
48:57the real world, like your mobile phone,
48:59your bicycle, the remote control of your
49:01TV, and so on. They have certain
49:02capabilities. So, if you type a string
49:05here,
49:06and then press dot, we can see all the
49:08functions or methods available in a
49:10string object in Python.
49:12Now, lists are also objects, so they
49:15have a bunch of methods for adding
49:16items, for removing them, and so on. Let
49:18me show you. So, I'm going to declare
49:21a list of numbers.
49:22Let's say one, two, three, four, and
49:24five.
49:25Now, to add a new element at the end of
49:27this list, we can use the append method.
49:30So, we type numbers
49:31dot append,
49:33and here we type six.
49:35Now, let's print our list.
49:39So, here's our updated list. Beautiful.
49:42Now, what if you want to insert a number
49:43somewhere in the middle or at the
49:45beginning?
49:46For that, we use the insert method.
49:49So, we're going to call the insert
49:51method.
49:52Now, on the top, go to the view menu,
49:55and look at parameter info. Look at the
49:58shortcut. On a Mac computer, it's
50:01command and P.
50:02On Windows, it's probably control and P.
50:05If we use this shortcut, we can see the
50:07values that this method expects.
50:10So, the first value that this method
50:12expects is an index value, and the type
50:15of this value is an integer.
50:16So, if you want to insert a value at the
50:18beginning of this list, I should pass
50:20zero as the index of the first element,
50:23right? So, let's pass zero.
50:25Now,
50:27the second value is highlighted. So, the
50:29second value is an object, and the type
50:31of this is T. That basically means this
50:34can be any type. We can pass a number,
50:36we can pass a boolean, we can pass a
50:38string, we can pass a list or any type
50:40of objects in Python.
50:42So, I'm going to pass -1.
50:45Now, let's run our program.
50:47We can see -1 appeared at the beginning
50:49of our list.
50:51We also have a method for removing
50:52items. So,
50:54let's call remove
50:56three.
50:57Let's run the program.
50:59Three is gone. We only have 1 2 4 and 5.
51:03Now, if you want to remove all the items
51:04in the list, we call the clear method.
51:06So, clear.
51:09This method doesn't expect any values.
51:11So, let's run our program. Our list is
51:13empty.
51:14Now, sometimes you want to know if a
51:16given item exists in our list or not. To
51:18do that, we use the in operator. So,
51:21let's remove this line.
51:24Instead of printing our numbers list,
51:25I'm going to print an expression.
51:28One
51:29in numbers.
51:31So, here we're using the in operator.
51:33We're checking to see if one is in the
51:35numbers list. So, this is a boolean
51:37expression. It returns a boolean value.
51:40Take a look.
51:41So, we get true.
51:43Obviously, if we search for a value that
51:45doesn't exist in this list, like 10,
51:48we get false, okay?
51:51Now, finally, there are times you want
51:52to know how many items you have in a
51:53list. To do that, you can use the
51:55built-in len function. So, let's print
52:00len of numbers. So, len is a built-in
52:04function, just like the print function.
52:06That is why it's highlighted as purple.
52:08It returns the number of elements in a
52:10list. Take a look.
52:13So, we have five elements in this list.
52:20When writing Python programs, there are
52:22times you want to iterate over a list
52:25and access each item individually. Let
52:27me show you.
52:28So, I'm going to declare
52:29a list of numbers,
52:311 2 3 4 5.
52:33Now, if we print this list,
52:36it comes out exactly like how we wrote
52:38it, using the square bracket notation.
52:41But, what if we wanted to print each
52:42item on a separate line?
52:44That is where we use the for loop. Let
52:46me show you. So, we're not going to
52:48print the entire list.
52:50Instead, we're going to type for.
52:52Now, we declare a variable, which is
52:53called a loop variable.
52:56Let's call it item.
52:57Then, we type in
52:59numbers.
53:00Next, we add a colon to start a block of
53:03code. So, this is what we call a for
53:05loop.
53:06With this for loop, we can iterate over
53:08all the items in this list. In each
53:11iteration, this item variable is going
53:13to hold one value. So, in the first
53:15iteration, item is going to be equal to
53:17one, in the second iteration is going to
53:19be equal to two, and so on.
53:21So,
53:22now if you print item
53:25and run our program,
53:26we see each item on a new line.
53:28So, this is how we use a for loop. Now,
53:31we could also achieve the same thing
53:32using a while loop, but our code would
53:34be a little bit longer. Let me show you.
53:37So, we would have to start by declaring
53:39a loop variable outside of our while
53:41loop. Let's say I. We set it to zero.
53:45Now, we say while I is less than
53:48Here, we need to find out how many items
53:49we have in this list.
53:51So, we use the len function.
53:53Len of numbers.
53:55So, as long as I is less than the length
53:58of the list,
53:59print
54:00Now, we can use the square bracket
54:02notation to get the element at this
54:04index. So,
54:06numbers of I.
54:10Now, we need to increment I by one. So,
54:13I equals I + 1.
54:15Let's run the program and see what we
54:16get.
54:19So, we get the numbers 1 to 5. These are
54:21coming out from our for loop. And then,
54:24we get the numbers 1 to 5 one more time.
54:26These are coming out from our while
54:27loop. Now, if you compare these two
54:29approaches, you can definitely see that
54:31the implementation using the for loop is
54:33shorter and easier to understand. We
54:35don't have to use the square bracket
54:37notation. We don't have to call the len
54:39function. We don't have to declare a
54:41variable, a loop variable, and then
54:43increment it explicitly. So, with the
54:46for loop, in each iteration, the item
54:48variable will automatically hold one
54:50value in this list.
54:58In this tutorial, we're going to talk
55:00about the range function in Python. We
55:02use the range function to generate a
55:04sequence of numbers. Let me show you.
55:06So, we type range.
55:08This is a built-in function, just like
55:10the print and input functions.
55:12Here, we can pass a value like five,
55:14and this will return a range object. A
55:17range object is an object that can store
55:19a sequence of numbers. Let me show you.
55:22So,
55:23let's call that numbers.
55:25So, this is a range object. In this
55:27object, we're going to have the numbers
55:29zero to five, but excluding five.
55:32Now, if we print
55:34numbers,
55:37we're going to see this message, range
55:39of zero to five, not the actual numbers,
55:41because this is the default
55:42representation of a range object. To see
55:45the actual numbers, we need to iterate
55:47over this range object using a for loop.
55:50In the last video, you learned how to
55:51iterate over a list using a for loop,
55:53but we can also iterate over a range
55:55object using a for loop. Basically, we
55:57can use the for loop with any object
56:00that represents a sequence of objects.
56:02So, instead of printing numbers,
56:05we're going to use a for loop.
56:07For number
56:08in numbers,
56:10colon,
56:11we're going to print
56:13number.
56:15Take a look.
56:17Now, we see the numbers zero to four.
56:20So,
56:21range of five
56:22generates a sequence of numbers starting
56:24from zero up to the number we specify
56:27here.
56:28Now, if we supply two values,
56:30the first value is going to be
56:32considered the starting value,
56:34and the second value is going to be
56:36considered the ending value, and it's
56:37going to be excluded. So, range of five
56:40to 10 is going to generate the numbers
56:42five to nine. Take a look.
56:45There you go.
56:46Now, we can also supply a third value,
56:49and that will be used as a step. So,
56:51let's say instead of having a sequence
56:53of numbers like 5 6 7 8 9, we want to
56:56jump two numbers at a time. So, 5 7 9,
56:59and so on.
57:00So, here we pass two as the step. Take a
57:03look.
57:05So, we get these odd numbers, 5 7 and 9.
57:10So, this is the range function in
57:11Python. Like quite often, you see the
57:13range function used as part of a for
57:15loop, because we don't really need to
57:17store the result in a separate variable.
57:19We can call the range function right
57:21here, where we are using the numbers
57:23variable. So, we can type range of five,
57:27and this will return a range object
57:29holding the numbers zero to four. Take a
57:31look.
57:32There you go.
57:34So, we don't really need to store the
57:35result in a separate variable like
57:37numbers.
57:39There you go.
57:47In this tutorial, we're going to talk
57:48about tuples in Python.
57:50Tuples are kind of like lists. We use
57:52them to store a sequence of objects, but
57:54tuples are immutable, which means we
57:57cannot change them once we create them.
57:59Let me show you.
58:00So, I'm going to start by defining a
58:02list of numbers, 1 2 3.
58:04Now, we use square brackets to define a
58:06list,
58:07and parentheses to define a tuple. So,
58:10now this numbers variable is storing a
58:12tuple.
58:13If we try
58:15to reassign, let's say the first
58:16element,
58:18we're going to get an error.
58:20Tuple object does not support item
58:22assignment.
58:23So, this is what I meant by tuples are
58:25immutable. They're unchangeable.
58:28Also,
58:30if we type numbers {dot}
58:32you don't see any methods like append,
58:34insert, remove, and so on. We only have
58:37count and index. Count returns the
58:40number of occurrences of an element. For
58:42example,
58:43if we have, let's say, two threes in
58:46this tuple,
58:47and call count of three, this will
58:49return two.
58:51The other method we have here is index,
58:53and this returns the index of the first
58:56occurrence of the given element.
58:58Now,
58:59these other methods you see here that
59:00start with an underscore, they're called
59:03magic methods. It's an advanced topic,
59:05and I've covered it in detail in my
59:06complete Python programming course. If
59:09you're interested, the link is down
59:11below this video.
59:12So, tuples are immutable. We cannot
59:14change them once we create them.
59:16Now, practically speaking, most of the
59:18time you would be using lists, but there
59:20are times that once you create a list of
59:21objects, you want to make sure that
59:23somewhere in your program, you or
59:25someone else is not going to
59:26accidentally modify that list. If that's
59:29the case, then you should use a tuple.
59:33Hey guys, I just wanted to let you know
59:34that I have an online coding school at
59:36codewithmosh.com where you can find
59:38plenty of courses on web and mobile
59:40development. In fact, I have a
59:41comprehensive Python course that teaches
59:44you everything about Python from the
59:45basics to more advanced concepts. So,
59:47after you watch this tutorial, if you
59:49want to learn more, you may want to look
59:50at my Python course. It comes with a
59:5230-day money-back guarantee and a
59:54certificate of completion you can add to
59:55your resume. In case you're interested,
59:57the link is below this video.
1:00:01Hey Mosh, hi Mosh.

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