Boolean functions

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Functions can return booleans, which is often convenient for hiding complicated tests inside functions. For example:

def is_divisible(x, y):
    if x % y == 0:
        return True
    else:
        return False

It is common to give boolean functions names that sound like yes/no questions; is_divisible returns either True or False to indicate whether x is divisible by y.

Here is an example:

>>> is_divisible(6, 4)False>>> is_divisible(6, 3)True

The result of the == operator is a boolean, so we can write the function more concisely by returning it directly:

def is_divisible(x, y):
    return x % y == 0

Boolean functions are often used in conditional statements:

if is_divisible(x, y):
    print 'x is divisible by y'

It might be tempting to write something like:

if is_divisible(x, y) == True:
    print 'x is divisible by y'

But the extra comparison is unnecessary.

Exercise 6.3.Write a function is_between(x, y, z)that returns Trueif x ≤ y ≤ z or False otherwise.