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- [Narrator] Next we're
going to take a look

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at a couple of methods that enable you

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to look at the characters within a string

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and see if they match
certain characteristics.

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Now those of you coming from
other programming languages

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may recognize methods or
functions like isdigit.

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In this case, in Python, isdigit is going

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to check every single
character within the string

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and see if that character is a digit.

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And only if all of them are digits

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will this method return true.

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So as you can see here, we get false

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because the minus sign
is not itself a digit.

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However, if I go ahead
and remove the minus sign

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and execute that, you can
see that indeed we get true.

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Now here's another one, the is A-L-N-U-M,

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is alphanumeric, so is
it a number or a letter.

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In this case, everything in this string

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is a number or a letter.

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And if I take a look at
another call similar to that,

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if we look at that briefly, we might say,

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yeah, those are all letters and numbers,

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but there's also a couple of spaces

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in this particular string,
so we get false on this one.

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So methods like these
can be used for example

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if you're validating data
either via user input

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or perhaps you're reading
data into an application

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to get ready to analyze it and you need

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to validate certain
fields within the data.

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And there's a whole bunch

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of these character testing methods.

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Let me just switch over to a
Adobe Acrobat PDF file here

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in which we have a table
of some of these methods.

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And I'm not going to read through

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all of them with you right now.

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If you'd like, you can go
ahead and pause the video

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and take a look at this
table, but as you can see,

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we have a number of different
methods that enable us

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to validate the characters
within a string.

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And then each of these
methods is going to return

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true or false depending on those values.