In this lesson we learn how to make create functions and how to treat them like a BLACK BOX, where we don't need to know the internals of them to use them.

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Writing functions and understand how data is passed to and from a function. We also introduce the __main__ function and show how to do basic tests on a function.

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In this lesson we look at more aspects of parameter passing, and how the return statement works. We also look at functions that don't return any values.

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Python maintains strict control on where a variable is in scope. In this lesson we review globally scoped variables, and scope in general, including dealing with variable name reuse.

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