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- [Instructor] In some cases,
you might find it necessary

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to raise exceptions
explicitly in your code.

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For example, if you are
defining your own functions that

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are going to be part of a
library that other people use,

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you may want to indicate exceptions

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when they use your library's
functions incorrectly.

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So to do that, Python
provides the raise statement

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and you simply follow the
raise keyword by the name

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of the exception class that
you want to create an object of

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and insert into the
exception handling mechanism.

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Now optionally, when you're
creating that exception object,

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you can supply parenthesis
following the class name.

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So for example, if you wanted
to give a custom error message

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for a particular exception
instance that you're creating,

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you would supply that as
an argument in parenthesis

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following the exception class
name in your raise statement,

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and by the way, before
you raise an exception,

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it's important that your code
de-allocate any resources

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that it acquired so those resources

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are handed back to the system properly.

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Now in general, you'll probably work with

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one of the many built-in exception types.

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You can find those at the URL

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shown at the bottom of this slide,

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but it is possible to create
your own new exception types

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as well which does require
creating new class definitions.

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That's part of what we'll be
discussing in the next lesson.