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In addition to membership testing, we can
also use methods to determine how many

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times a given object
appears in a sequence.

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And then finally, where or what index
a particular object falls in a sequence.

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A method is just a function that
is called on a specific object.

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Sequences, like most everything in Python,
are objects.

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And they have special methods
that can be called on them.

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For the first part of this video,
we'll be talking about the count method.

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Count is a built-in sequence method.

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It receives one argument,
the object that we're counting.

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Let's pick up with the last example.

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Now that we know the string
tuple is inside docs,

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let's figure out how
many times it appears.

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To use the count method,

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we'll first provide the sequence
we wish to count from.

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Then we have a dot and
then the name of the method,

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Followed by parens,
just like with regular functions.

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And then we pass in our argument,
which is the string tuple.

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All of this code together says that we
want to know how many times the string

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tuple occurs in docs.

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I'll wrap this in a print statement so
we can see the result, and

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then I'll save it and run it.

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Okay, the Python interpreter says that
the count method returned the number 1,

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meaning the string tuple appears
in this excerpt one time.

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But I'm looking at it right now, and
I see tuple in there three times.

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Is the method wrong?

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Nope, all of these operators and
methods are looking for exact matches.

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When it comes to strings,
that means everything is case sensitive.

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This excerpt only includes the string
tuple with a lower case t one time.

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Both other times,
tuple begins with a capital t, and

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thus aren't considered a match.

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See the following instruction step for

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more examples on how to use count
with different sequence types.

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Python also gives us a way to find the
index of the first occurrence of an object

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inside a sequence.

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This is done using the index method.

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The syntax is very similar
to the count method.

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And just like the count method,

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the index method takes a single argument,
the object we want to find.

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So in our example here,
I'll just change count to index.

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Then I'll save it and run it.

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Cool, it printed out 105.

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What does that mean?

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It means that the lowercase string tuple
is first found at the 105 index in

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the docs string.

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Or in other words, our matched tuple
string starts at the 106th character.

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I'm gonna erase all this and

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show another example of the index
method with a short list.

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Here, I'm going to make an alphabetized
list of a few Treehouse teachers.

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I want to find the index that
Nicole appears in this list.

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So to do that, I'll do teachers.index,

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and then I'll pass Nicole as my argument.

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I'll wrap this in a print statement.

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And then now we'll run.

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Okay, this code printed out the number 2,

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meaning that the index of the item
that matches Nicole is 2.

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That makes sense, we can see that Nicole
is the third element in the list.

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So what happens if we add Nicole's
name to the list a second time?

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Let's run this again.

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It's still printing out 2.

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That's because the index method only
returns the index of the very first

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occurrence of an object, no matter how
many times its present in a sequence.

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And now what happens if we delete
the Nicole items from the list altogether?

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Okay, we're getting a ValueError.

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It says, 'Nicole' does not exist in list.

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This is important to remember.

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If you're using this method,
always account for

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the fact that if the object doesn't exist,
you'll get an error, not an integer.

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And your code won't run.

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All right, when you're ready, join me
in the final video of Python Sequences

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to learn about concatenation and
multiplication.