Name: Lesson 3 - Python Programming (Automate the Boring Stuff with Python)
Uploaded: 2018-09-11T17:57:05.000Z
Duration: 10 min 3 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

That's enough for the interactive shell for now. Let's write our first program.

This makes the file editor window appear.

Enter the following code: I'll ex[plain what it  does afterwards.

' in a year.' Save this program as hello.py.

Python programs are just text files that have the .py

Run Module or just press F5 to run the program.

"It is good to meet you Al. The length of your name is

Okay, that's the entire program. One thing to keep in mind

is that Python will start at the first instruction at the top of the program,

and then move downwards executing each instruction entered

Think of it as putting your finger on the top instruction

and as each instruction is executed moving your finger

down to the next instruction. This is just like how you might move your finger

along the lines of a book that you're reading.

Your finger is called the execution. The execution

in Python starts at the top and moves down.

pound sign is called a "comment". Python ignores comments.

You can use them to write notes to yourself or reminders

about what the code is trying to do or what the entire program does.

Blank lines are completely ignored by Python. You can just use these to space

In fact, let's add a couple more blank line right here

code that's relevant to asking for your name, and

print() function displays the string value inside the parentheses

on the screen. So the line print('Hello world!')

means print out the text in the string 'Hello World!'.

Functions in Python are like mini-programs in your program.

They contain code that you various things and for your convenience Python

arguments. But really, values and arguments are the exact same thing.

This is called calling the print() function.

We have code like this here. So the next instruction is also a call

the print() function. This time it's passing the 'What is your name?'

string to the print() function. There's also a comment at the very end of the

to the end of an instruction since everything after that

pound sign will just be ignored by Python. When the input function

is called, Python waits for the user to type some text on a keyboard and

Just like a variable will evaluate to the value it contains,

calls to the input() function evaluate to the string value

myName variable assignment statement would just evaluate to 'Al'.

And then the string will get stored inside myName.

Remember, expressions can always evaluate down to a single value.

and this is what that call to the print() function looks like

first my name evaluates to the value inside it

and then, this is just a string concatenation,

This is the string that gets passed to the print() function call.

This next line introduces a new function called

len(). What len() does is it takes a string

to the integer value of the length of the string,

which is the number characters in a string. Let's just experiment with this

function in the interactive shell for a little bit.

so I can call the len() function and pass it

length... the blank string and that returns 0.

and then I can just use these function calls to len() anywhere

I could using integer. So I could say, you know,

type out my name ten times, it's length would be 20.

So then we have some more print() and input() calls.

This time we're saving whatever the user types

into the variable myAge. And then we have this line,

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