Real Python Doubling solution

# started 11:44 am
# rev1: 11:55 am
# refactored: 12:08 pm

import random

# -------------------------------------------
# Doubling challenge spec
# -------------------------------------------
# Doubling
# - Create a list of numbers, save it to a variable
# - Pass this list to a function called double()
# - Use a for loop to iterate through each element of the list
# - Write a separate (helper) function, doubling(), that returns any number it is given multiplied by two
# - Pass each element from the for loop to this helper function
# - Save the original numbers and the doubled results as key-value pairs in a dictionary
#

def doubling(n):
    '''This makes more sense if named double(n)'''
    return n * 2

def double(numbers):
    '''
    Doubles each n, returns them in a dict.
    Spec is ambiguous as to whether they wanted this in one or a composition of functions ;)

:param numbers: a list of numbers to double
    :return A dict of n -> (n*2) for each n in numbers

(This would be more idiomatic as a list comprehension)
    Implementation per challenge spec
    - Use a for loop to iterate through each element of the list
    - Write a separate (helper) function, doubling(), that returns any number it is given multiplied by two
    - Pass each element from the for loop to this helper function
    - Save the original numbers and the doubled results as key-value pairs in a dictionary
    '''
    doubled = []
    for n in numbers:
        doubled.append(doubling(n))
    return dict([ (n, d) for n, d in zip(numbers, doubled) ])

# -------------------------------------------
# Refactored and rewritten to be more idiomatic.
# -------------------------------------------
#   Using _foo prefixing to avoid conflicting with the challenge spec

def _double(n):
    '''Returns two times a number'''
    return n*2

def double_list(numbers):
    '''
    Doubles each n, returns them in a list.

:param numbers: a list of numbers to double
    :return A list of 2n
    '''
    return [ _double(n) for n in numbers ]

def double_list_into_dict(numbers):
    '''
    Doubles each n, returns them in a dict.

:param numbers: a list of numbers to double
    :return A dict of n -> (n*2) for each n in numbers
    '''
    # We could reduce numbers into set(numbers) so that we avoid processing the same thing more than once:
    # e.g.: return dict([ (n, doubling(n)) for n in set(numbers) ])
    return dict([ (n, d) for n, d in zip(numbers, double_list(numbers)) ])

# -------------------------------------------
# Driver
# -------------------------------------------

def main():
    numbers = [ random.randrange(1,25) for i in range(1,12) ]
    # numbers = [ 0, 1, 2, 3, 4, 5 ]
    doubled = double(numbers)
    print "Doubling per Challenge spec:"
    print(doubled)
    print "Doubling refactored:"
    print(double_list_into_dict(numbers))

if __name__ == '__main__':
    main()

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