Python course / Foundations

Loops

Repeat work with while and for, and walk a sequence while keeping totals, positions and flags straight. Loops are where beginners lose the most time, usually to a stop condition that never fires or a total started in the wrong place.

while
for
range
break and continue
enumerate
zip
running totals
flags

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a running total and a position

readings = [4, 7, 7, 2, 9]

total = 0
highest = readings[0]
for position, value in enumerate(readings, start=1):
    total += value
    if value > highest:
        highest = value
    print(f"reading {position}: {value}")

print("total:", total)
print("highest:", highest)

reading 1: 4
reading 2: 7
reading 3: 7
reading 4: 2
reading 5: 9
total: 29
highest: 9

What you will learn

Repeat a block for as long as a condition holds.
Loop over a sequence of numbers, with the stop excluded.
Stop a loop as soon as it has found what it was looking for.
Loop over items and their positions together.
Walk two lists side by side, and notice when they do not line up.
Join pieces into one string without a stray separator at the end.

The lessons in this module

while
Loops that never end
for over a string
range
Steps and counting down
Running totals
Biggest and smallest
break
continue
Controlling the step yourself
Nested loops
for with else
enumerate
zip
Asking until the answer is valid
Reading until a stop word
Reading in the condition
Backwards and by position
Building text in a loop
Several results in one pass
Watching a loop run
Remembering the previous item
Flags that stay set
Module review: receipt reader

Ready when you are

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