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6.4: Boolean functions

  • Page ID
    40888
  • 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.

    As an exercise, write a function is_between(x, y, z) that returns True if \( x \leq y \leq z \) or False otherwise.

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