# Python Lessons – 3.2 Functions

## Functions

You have already seen and used the functions in the previous parts of the course. It is called a function call whenever we have used the following expression:

function_name()

For example, there are some features that we have already seen before

• print(“Hello World”)
• range(10)
• max()

The word that precedes the parentheses is the function name, while the values or variables within the brackets are called arguments.

## Function definition

So far you have seen and worked with already defined functions, but functions can be created using def.

You define a simple function that prints the first 5 numbers of the Fibonacci sequence

``````def fibonacci():
i = 1
n1 = 0
n2 = 1
print ( n1 + n2)
while i < 10:
n = n1 + n2
print( n )
n1 = n2
n2 = n
i += 1

fibonacci()``````

Executing the function you will obtain the sequence of the first 10 numbers of the Fibonacci sequence:

``````>>>
1
1
2
3
5
8
13
21
34
55``````

⇐ Go to Python Lesson 3.1 – Functions and modules – Code Reuse

Go to Python Lesson 3.3 – Functions arguments ⇒

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