Series: Modules

Let's talk about importing modules in Python.

Also see the

moduledefinition in Python Terminology.

Python comes bundled with a whole bunch of modules called the Python standard library.
We're going to import the `math`

module from the standard library:

```
>>> import math
```

The `math`

module has a function called `sqrt`

that we can use to get the square root of a number.

We can't currently call the `sqrt`

function directly:

```
>>> sqrt(25)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'sqrt' is not defined
```

To use the `sqrt`

function need to call `math.sqrt`

:

```
>>> math.sqrt(25)
5.0
```

Whenever you import a module, Python will make just one variable, the name of the module that we imported, (`math`

in our case) which points to a module object:

```
>>> math
<module 'math' from '/usr/lib/python3.9/lib-dynload/math.cpython-39-x86_64-linux-gnu.so'>
```

When we imported the `math`

module, we got **a module object**, and that module object **has attributes**.

Our `math`

module object has a `pi`

attribute:

```
>>> math.pi
3.141592653589793
```

And an `e`

attribute:

```
>>> math.e
2.718281828459045
```

And a `sqrt`

attribute:

```
>>> math.sqrt
<built-in function sqrt>
>>> math.sqrt(25)
5.0
```

And a whole bunch of other attributes.
Everything within the `math`

module lives as an attribute on that `math`

module object.

After you've imported the `math`

module, you'll need to put `math.`

before the name of anything you'd like to use in the module.
If you don't want to have to type `math.`

something every time you use something in the `math`

module, instead of using an `import`

statement you could use a `from`

-`import`

statement.

So instead of this:

```
>>> import math
```

You could do this:

```
>>> from math import sqrt
```

Now we'll have access to the `sqrt`

function directly:

```
>>> sqrt(25)
5.0
```

Or if we wanted to import multiple things we could put commas between them:

```
>>> from math import sqrt, pi
```

We now have `pi`

and `sqrt`

:

```
>>> pi
3.141592653589793
>>> sqrt(25)
5.0
```

but we don't have `e`

:

```
>>> e
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'e' is not defined
```

Because we didn't import `e`

from the `math`

module.

See 4 ways to import a module in Python for more on importing.

If you want to import a module in Python, you'll need to use an `import`

statement.
But unless you want to type the name of the module over and over (each time you access something in the module), you might want to use the `from`

syntax for importing instead: `from MODULE_NAME import THINGS_FROM_MODULE`

.

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Modules are the tool we use for breaking up our code into multiple files in Python.
When you write a `.py`

file, you're making a Python module.
You can import your own modules, modules included in the Python standard library, or modules in third-party packages.

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