# Python Functions

A function is a block of code that only runs when it is called. You can pass data, known as parameters, into a function. A function can return data as a result.

## Creating a Function

In Python, a function is defined using the `def` keyword.

```python
def my_function():
  print("Hello from a function")
```

## Calling a Function

To call a function, use the function name followed by parenthesis.

```python
my_function()
```

## Parameters

Information can be passed to functions as parameters.

```python
def my_function(fname):
  print(fname + " Refsnes")

my_function("Emil")
my_function("Tobias")
my_function("Linus")
```

## Return Values

To let a function return a value, use the `return` statement.

```python
def my_function(x):
  return 5 * x

print(my_function(3))
print(my_function(5))
print(my_function(9))
```