String methods in Python are easy 〰️

PROFESSOR: Hey, everybody.

In this topic, I'm going to
cover a few useful string

methods that you may
be interested in.

Then at the end of this video,
we will work on an exercise

where we will validate
some user input.

As we know, a string is
just a series of characters.

Let's ask a user
for their full name.

Name equals input.

Enter your full name.

The first method I'll show you.

Well, technically
this is a function.

The length function will give
us the length of a string--

how many characters is it.

We will find the length
of our variable name

after the user
types in some input.

This function
returns an integer.

I'll store that result
within a variable.

Let's just say
result. Then I will

print whatever the result is.

Why don't you go ahead and
type in your full name?

The length of this string in
my example is eight characters.

That does include spaces, too--

1, 2, 3, 4, 5, 6, 7, 8.

If you ever need the
length of a string,

there is the length function.

Let's move on.

If we were to type our variable
name followed by a dot,

we have access to a whole
bunch of different methods.

We have the find method.

The find method will return
the first occurrence of a given

character-- the position.

Let's find any spaces.

I'll store the result within
a variable named result.

I will type in my full name.

The first occurrence of a
space, that's what we set,

is at position 3.

When working with indexes,
we always begin with 0.

This first character would have
an index of 0, then 1, 2, 3.

That's why the find method
returned 3 in place of 4.

Let's find the first
occurrence of a capital B.

See, it's 0.

How about.-- oh, for
me, that would be 2.

So remember, it's always
the first occurrence.

If you need the last
occurrence, there

is a different method, which
is rfind, r meaning reverse.

We will find the last
occurrence of an o.

That has a position of 5--

0, 1, 2, 3, 4, 5.

If Python isn't able to
locate a given character,

it will return negative 1.

Let's find any--

I don't know-- q's.

Python could not find
any lowercase because.

The rfind method will
return negative 1

if there are no results.

We can capitalize the
first letter in a string

by using the
capitalize function.

Name.capitalize-- this
method will return a string.

I will reassign that to name.

Then we will print
our name capitalized.

I'll be sure to type in
my name, all lowercase.

Since this is all one
string, only the first letter

is capitalized, even though I'm
including a first and last name.

The upper method will take all
of the characters in a string,

then make them all uppercase
Follow your variable that

contains a string
followed by .upper.

Then I will reassign the
result to my name variable

to overwrite it.

Enter your full name.

All of the letters
are now uppercase.

There is also lower to make all
of the characters lowercase.

Name equals name dot lower.

Yep, all the characters
are lowercase now.

The isdigit method will
return either true or false

if a string contains
only digits.

The result is a Boolean--

true or false.

I'll store that within
a variable named result,

then print result.

So if I were to type in my full
name, isdigit returns false.

There are not only digits
within that string.

If my string was
some combination

of alphabetical
characters and numbers,

this method will
still return false.

It only returns true if my
string only contains digits.

I'll just type in 1, 2, 3.

See, that's true.

That is the isdigit method.

Otherwise, we have isalpha--

name.isalpha.

The isalpha method
will return a Boolean--

true or false-- depending
if a string contains

only alphabetical characters.

I'll type in my full name.

So the reason that
this came up false

is because my full name
contains a space, which is not

an alphabetical character.

If I typed in my full
name, excluding any spaces,

this would now be true.

isalpha would also return
false if my name contained

any sort of digits--

0, 1, 2, 3.

And that is also false.

That is the isalpha method.

Now let's ask for
a phone number.

Phone number equals input.

Enter your phone number.

With the phone number, they
typically contain dashes.

Let's count how many dashes are
going to be in somebody's phone

number.

Phone number dot count method.

Let's count the
amount of dashes.

So place a character
within the count method.

This method will
return an integer.

Let's store that
within a variable.

Result equals phone
number dot count method.

So type in some phone number--

1-234-567-8901.

We have three dashes
within the string--

1, 2, 3.

That is the count method.

We can count how many
characters are within a string.

We also have the replace method.

Honestly, the replace
method is probably

one of the most useful
methods of strings.

We can replace any occurrence
with one character with another.

Replace.

Let's replace any dashes
with maybe a space.

This method will
return a new string.

I'm going to reassign this
to our phone number variable,

then print the phone number.

Enter your phone number.--

1-234-567-8901.

So here's my new phone number.

But we've replaced all of
the dashes with spaces.

Even better yet, we could
eliminate all the dashes

completely by replacing the
dashes or another character

with an empty string.

1-234-567-8901.

Here's our new phone
number without any dashes.

We've replaced all dashes
with an empty string.

No characters.

If you would like a
comprehensive list of all

of the string methods
available to you,

you can use the help function.

Type in the data type
str meaning string.

Then I will print
whatever the result is.

Here's a bunch of
methods you might

be interested in the future--

capitalize, casefold, center,
count, encode, endswith--

just to name a few.

All right, everybody,
here's an exercise for you.

We will validate
some user input.

We would like a user to
enter in a valid username.

However, there's a couple rules.

The username can be no more
than 12 characters long.

The username must not
contain any spaces,

and the username must
not contain any digits.

Let's assign a variable
named username equals input.

Enter a username.

First, let's check to
see if our user input is

more than 12 characters long.

We can do that using
the length function.

We will find the
length of our username.

The length function
returns an integer.

Let's check to see if the
length of our username

is greater than 12 characters.

If it is, we'll print a message.

Your username can't be
more than 12 characters,

else we will print
using an f string--

welcome, whatever our
username variable is.

Let's try it.

I'll type in my first
name, last name, then

add a whole bunch of
characters afterwards.

Your username can't be
more than 12 characters.

Let's type in something
that's under 12 characters.

Yep, and that appears to work.

OK, so we have
accomplished task number 1.

Our username can't be
more than 12 characters.

Next, our username must
not contain any spaces.

We can use the find
method of a string.

Username.find-- we
will find any spaces.

That's a character.

If no spaces are found, this
method will return negative 1.

Using an elseif
statement, I'll add

not if the find method of
username equals negative 1.

If the result is not negative
1, meaning we found a space,

we will print your username
can't contain spaces.

I'll type in my
first and last name.

You might need to think
of something that's

underneath 12 characters.

Your username can't
contain spaces.

So we have accomplished
rule number 2.

Three, username must
not contain digits.

We can use the isalpha
method of strings.

The isalpha method
returns a Boolean

if a string only contains
alphabetical characters.

So let's copy that.

I'll add another
elseif statement,

not username is alpha.

Then we will print your
username can't contain numbers.

I guess technically, isalpha
would check for spaces, too,

but I'd rather have that be
handled within a different if

statement.

All right, I'll
type in a username.

I'll include some digits.

Your username can't
contain numbers.

All right.

I think we've accomplished this.

Let me make up a username
following these three rules.

Yep.

It seems to check out.

All right, everybody.

And that is a few
useful string methods

that you may be interested in.