beginner25 min
Control Flow
Making decisions with if/else and repeating with loops
Making Decisions: if/elif/else
Programs need to make decisions. Python uses if, elif (else if), and else:
Basic if/else
Output
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Important: Indentation Matters!
Python uses indentation (spaces at the start of a line) to define blocks of code. The standard is 4 spaces. Every line inside an if block must be indented at the same level.
Comparison Operators
Output
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Logical Operators
Combine conditions with and, or, not:
Logical Operators
Output
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Loops: Doing Things Repeatedly
For Loops
Use for to iterate over a sequence:
For Loop Basics
Output
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While Loops
Use while to repeat as long as a condition is true:
While Loop
Output
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Check Your Understanding
What keyword do you use for 'else if' in Python?
Check Your Understanding
How many times will this loop run: `for i in range(3):`?
Exercise
Write a program that prints all even numbers from 2 to 20 (inclusive). Use a for loop and an if statement to check if a number is even (hint: use the modulo operator `%`).
Python will load on first run