Making decisions

Code that decides

An if statement runs a block of code only when a condition is true.

score = 72

if score >= 50:
    print("Pass")
else:
    print("Try again")

Two details are important in Python:

• The line with if or else ends with a colon :.
• The block under it is indented, usually with four spaces. The indent is how Python knows which lines belong to the block.

Comparison operators

Operator	Meaning
==	is equal to
!=	is not equal to
> and <	greater than, less than
>= and <=	greater than or equal to, less than or equal to

Use two equal signs, ==, to compare. One equal sign, =, stores a value in a variable.

and, or, not

You can join conditions with words.

• a and b is true when both are true.
• a or b is true when at least one is true.
• not a turns True into False, and False into True.

More than two paths

Use elif (short for "else if") to add more conditions. Python checks them from top to bottom and runs the first block whose condition is true.

Functions in this lesson

The editor has four functions. A function is a named block of code. You can give it values, and it gives a value back with return. You will write your own functions in lesson 8. For now, replace the word pass in each function with your code. The checker calls each function with many values, so your code must work for all of them.

def double(n):
    return n * 2

Your turn

Do the four tasks in order.