Python: Function

By Xah Lee. Date: . Last updated: .

Here's a example of defining a function.

def ff(x, y):
    """ff(x, y) returns x+y."""
    return x+y

print(ff(3,4))
# 7

A string immediately following the function def line is the function's documentation.

return is optional. If a function does not return statement, it returns None.

Unspecified Number of Positional Parameters (Aka Rest Parameters)

To define unspecified number of positional parameters, use *name as last item. Your function will receive it as a Tuple .

💡 TIP: this is useful if you need to define a function such as sum. 

# function with unspecified number of args
def ff(*x):
    # x is received as a tuple.
    return x

rr = ff(5,6)

print(rr)
# (5, 6)

print(type(rr))
# <class 'tuple'>

# example of position param with rest param
def ff(a, *x):
    return [a, x]

rr = ff(5, 6, 7)

print(rr == [5, (6, 7)])
# [5, (6, 7)]

Python Function and Class