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In this video, we'll be discussing
membership testing, in other words,

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whether or not an item or
sequence is inside another sequence.

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Membership testing uses
the operators in and not in.

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Take a look at my workspace here,
you can see I have a really long string,

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really an entire paragraph
from the Python documentation.

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I want to know whether this documentation
excerpt contains the string tuple.

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To find that out,
I can use the operator in.

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The expression, 'tuple' in docs,
will evaluate to true or

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false, true if tuple appears in docs,
and false if it does not.

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You'll see this expression most often
used in conjunction with an if statement.

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So I'm gonna add just a little
bit of code to this, and

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then we're gonna run it
to see what happens.

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Okay, save and run.

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Great, this tells us that the string tuple
is in fact inside this longer string docs.

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Alternatively, we can
use the not in operator.

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This is the opposite of the in operator.

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Not in will return true if the tested
object is not in the sequence, and

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will return false if it is.

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To demonstrate this, I'll modify
our example code just a little bit.

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I'll change the in operator to not in, and
then I'll change our print statements.

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Now when we run this again,
we should see the same result.

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Yes, the string tuple is present
inside the larger string docs.

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That's the gist of membership testing.

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I've demonstrated it here with strings,
but

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these operators work for all sequences.

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See the following instruction step for
code examples showing how to use in and

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not in with lists and tuples as well.