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list processing

For loops work with lists of any size

Python’s for loop exists to process lists and other iterations in Python. Lists are
the most common iterated data structure in Python, and when you need to
iterate a list, it’s best to use for:
The keyword “for” The keyword “in” separates A colon “:” follows your
indicates the start the target identifier from list name and indicates
of the loop and your list. the start of your list-
comes before the processing code.
target identifier.
for in :
target identifer
list

list-processing code

The list-processing code
MUST be indented
under the for loop.

The list-processing code is referred to by Python programmers as the suite.
The target identifier is like any other name in your code. As your list is
iterated over, the target identifier is assigned each of the data values in your
list, in turn. This means that each time the loop code executes, the target
identifier refers to a different data value. The loop keeps iterating until it
exhausts all of your list’s data, no matter how big or small your list is.
An alternative to using for is to code the iteration with a while loop.
Consider these two snippets of Python code, which perform the same action:
When you use “while”,
you have to worry about
“state information,” count = 0
which requires you while count < len(movies): for each_item in movies:
to employ a counting print(movies[count]) print(each_item)
identifier. count = count+1

When you use “for”, the
Python interpreter
worries about the “state
These while and for statements do the same thing. information” for you.

16 Chapter 1