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- [Instructor] Next let's
take a look at replacing

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and splitting sub strings.

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Now previously, we've talked
about various string methods

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that enable you to do searching
and replacing and splitting.

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But in the context of regular expressions,

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you have more power because
you can look for complex

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patterns to either replace
or split larger strings at.

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So as you can see, we've
already imported the re module.

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And let's take a look at
our first expression here.

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In this case, the
expression that we're going

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to be looking for is a tab character,

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and we're going to be replacing
tab characters in the string

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that we're going to
search with comma spaces.

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So every tab will be replaced
with a comma and a space.

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And this is the string
in which we are going

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to perform the operation.

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So you can see here, we
have three tab characters

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and if I execute that it
returns to me a string

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in which every tab has been
replaced by a comma and a space.

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And if for any reason you
have the need to limit

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the total number of replacements,

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you can use the count keyword argument.

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So if I say I only want to
replace the first two tabs,

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with commas and spaces, I can do that.

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In which case, the last
piece of the original string

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is left in tact.

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So that's regular expression substitution,

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with the sub function from the re module.

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Now let's talk about splitting a string

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using the regular expression
version of the split function.

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So the string type has a split method,

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that will operate on whichever
string you call split upon.

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Here we're passing in the
regular expression to search for,

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and the string that should be split.

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So let's take a look at our
regular expression first here.

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You can see that we have a raw
string consisting of a comma.

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Which is a literal value.

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Followed by, a back slash s,

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which is the character class
for white space characters,

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and asterisk quantifier.

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So what this says is,
I'm going to have a comma

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followed by zero or more
white space characters.

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Well if you look at the string

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in which we're going to search,
in this case we have a comma

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followed by two white space characters.

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A comma followed by two
white space characters,

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a comma followed by zero
white space characters,

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a comma followed by a
bunch of white space,

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and then a couple more commas

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with no white spaces following them.

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So this pattern is going
to match every case

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in which we have commas in this string

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and any number of space
characters from zero

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to as many as necessary to
replace all of those commas.

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And remove them from the string

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to create a list of sub strings.

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So when I do that you can see
we're able to very quickly

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parse out all of the values
from this comma separated list

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that had awkward spacing within it.

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Now just like we did up above,
we have a keyword argument

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that we can use, that enables
us to specify the maximum

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number of splits.

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It's called max split, and if I set that,

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let's say to three.

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Then it will only split
in the first three matches

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of the regular expression
and then the remainder

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of the string will
become the in this case,

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fourth element of the resulting list.

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So we get one, two, and three,

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and then this is the remainder
of the resulting string.