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Welcome back. In this lesson,

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we're going to highlight a few subtleties with functions including: that

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each execution gets a fresh set of

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local variables that disappear at the end of the function execution,

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that functions can call other functions,

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and that functions can have side effects on mutable objects.

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At the end of this lesson, you should be able to, one,

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avoid the use of global variables and function definitions by

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creating formal parameters for all values that are needed,

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and two, identify whether a function has any side effects,

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Including mutations to lists and dictionaries. We'll see you at the end.