# First function

Created by Julien Palard

Write a function computing the perimeter of a circle given its radius.

Your function should be named `circle_perimeter(radius)`, where the `radius` parameter is the radius of a cirle.

Your function should return the perimeter of a circle of the given `radius`.

To test it, we will import your function and try it with different values, such as:

``````>>> circle_perimeter(1)
6.283185307179586
>>> circle_perimeter(10)
62.83185307179586
>>> circle_perimeter(100)
628.3185307179587
``````

## Functions

For example, here is a simple function which takes a value and give it back unmodified:

``````def identity(x):
return x
``````

We can call our `identity` function and check it gave us back the given value:

``````>>> identity(42) == 42
True
``````

So:

``````>>> print(42)
42
``````

and:

``````>>> print(identity(42))
42
``````

are behaving the same. In the first case, we give `42` to `print`, which prints "42". In the 2nd example we give `42` to `identity`, which gives back `42`, which is directly given to `print`, printing "42" again.

We could also compare those equivalent codes:

``````>>> fourty_two = 42
>>> print(fourty_two)
``````
``````>>> fourty_two = identity(42)
>>> print(fourty_two)
``````
``````>>> fourty_two = 42
>>> fourty_two = identity(fourty_two)
>>> print(fourty_two)
``````

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