Functions

Functions are used to define a block of code that can be called several times. print, input and len are global functions provided by Python. Likewise, we can define our own functions.

Functions can have 0 or more parameters:

# Definition
def greet(name):
  print("Hello " + name + "!")


# Use it
greet("Peter") # Hello Peter!

Use the return keyword to define the value that will be available in the outer scope when the function finishes running.

# a and b are function arguments
def add_numbers(a, b):
  return a + b

result = add_numbers(1,2)
print(result) # 3

Common uses of functions are:

1. Avoid repetition by defining the same logic once and calling it when needed. See DRY
2. Code organization: give a meaningful name to parts of the code that are maybe too long.