introduction.md

Introduction

Python has two looping constructs. while loops for indefinite (uncounted) iteration and for loops for definite, (counted) iteration. The keywords break, continue, and else help customize loop behavior. The range(<length of sequence>) and enumerate(<iterable>) functions help with loop counting and indexing.

while loops do not have a number of loops to execute specified, and will continue as long as the loop expression or "test" evaluates to True. The loop will terminate when the loop expression evaluates to False.

while expression:
    set_of_statements

for loops cycle through the values of any sequence, terminating when there are no more values returned. The range(<length of sequence>) function provides a loop counter or sequence when there is no data structure or other iterable to loop over.

# Python will keep track of the loop count internally.
for item in sequence:
    set_of_statements
    
# `range()` is used as an explicit loop counter.  
# This will loop 12 times, from index 0 to index 11.
for item in range(12):
    set_of_statements