# 16.9: Variables and Parameters Are Local

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When you create a variable inside a function, it is local, which means that it only exists inside the function. For example:

def cat_twice(part1, part2):
cat = part1 + part2
print_twice(cat)


This function takes two arguments, concatenates them, and prints the result twice. Here is an example that uses it:

>>> line1 = 'Bing tiddle '
>>> line2 = 'tiddle bang.'
>>> cat_twice(line1, line2)
Bing tiddle tiddle bang.
Bing tiddle tiddle bang.


When cat_twice terminates, the variable cat is destroyed. If we try to print it, we get an exception:

>>> print cat
NameError: name 'cat' is not defined


Parameters are also local. For example, outside print_twice, there is no such thing as bruce.

This page titled 16.9: Variables and Parameters Are Local is shared under a CC BY-NC-SA 3.0 license and was authored, remixed, and/or curated by Allen B. Downey (Green Tea Press) .