for Loops

Iteration over … Something

Iteration: a central concept everywhere

• Programs build and manipulate data

• … and occasionally (most often?) iterate over data

• ⟶ Specialized looping construct: for

for name in ['Caro', 'Johanna', 'Eva', 'Jörg']:
    print(name)

• name: loop variable

• Bound to the current element in the list, four times in a row

• A list is iterable - many other types participate in this game

break, continue, else

Just as with while: usual looping features

• break ends the loop - else clause not executed

• continue executes block with next element (if any)

haystack = ['straw', 'mouse', 'straw', 'needle', 'straw']
for item in haystack:
    if item == 'needle':
        break
else:
    print("couldn't find needle")