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 catNameError: name 'cat' is not defined

Figure 3.1 Stack diagram. 

 

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