Python L∞ps
What is a Loop?
Automates repetitive tasks
For Loop
Iterates/traverses over a sequence (list, tuple, string)
each item in sequence
Last item reached?
Y/N
Back to sequence
Yes
No
Exit Loop
For Loop
- Used to run your code a specific number of times
- For loops starts with the keyword for
- A variable follows the keyword for that takes the value of the item inside the sequence on each iteration
- The body of the for loop is indented
For Loop
Looping through items in a tuple
Looping through characters in a string
Generate a series of numbers
range ( ) function
- The range ( ) function generates a series of numbers
- Example 1 prints numbers from 0 through 10
- Example 2 prints numbers from 1 through 10
- The output will never contain the end value
List of Numbers using the
range ( ) function
While Loop
Keeps running as long as the condition is true.
Enter While Loop
Condition
T/F
Back to Condition
False
True
Exit Loop
While Loop
- Used when you don't know beforehand the number of times to iterate
- While loops starts with the keyword while
- The condition is checked first and only enters the loop body if the condition evaluates to true
- Process continues until the condition evaluates to false
- Infinite loop occurs when the condition never evaluates to false
Break and Continue
- When you want to terminate the current iteration or the entire loop without checking the test condition
Alternating the flow of a loop
Break Statement
Terminates the loop
Condition
T/F
Break
Y/N
Back to Condition
Enter Loop
False
True
Yes
No
Exit Loop
Break Statement
Break statement in a for loop
Break statement in a while loop
Continue Statement
Skips the current code block and returns back to the loop
Condition
T/F
Continue
Y/N
Back to Condition
Enter Loop
False
True
Yes
No
Exit Loop
Continue Statement
Continue statement in a for loop
Continue statement in a while loop
practice!
Python Loops
By vic_lee
