Mapping values of different iterables

For example calculating the average of each i-th element of multiple iterables:

def average(*args):
    return float(sum(args)) / len(args)  # cast to float - only mandatory for python 2.x

measurement1 = [100, 111, 99, 97]
measurement2 = [102, 117, 91, 102]
measurement3 = [104, 102, 95, 101]

list(map(average, measurement1, measurement2, measurement3))
# Out: [102.0, 110.0, 95.0, 100.0]

There are different requirements if more than one iterable is passed to map depending on the version of python:

The function must take as many parameters as there are iterables:

def median_of_three(a, b, c):
    return sorted((a, b, c))[1]

list(map(median_of_three, measurement1, measurement2))

TypeError: median_of_three() missing 1 required positional argument: ‘c’

list(map(median_of_three, measurement1, measurement2, measurement3, measurement3))

TypeError: median_of_three() takes 3 positional arguments but 4 were given

map: The mapping iterates as long as one iterable is still not fully consumed but assumes None from the fully consumed iterables:

import operator

measurement1 = [100, 111, 99, 97]
measurement2 = [102, 117]

# Calculate difference between elements
list(map(operator.sub, measurement1, measurement2))

TypeError: unsupported operand type(s) for -: ‘int’ and ‘NoneType’

itertools.imap and future_builtins.map: The mapping stops as soon as one iterable stops:

import operator
from itertools import imap

measurement1 = [100, 111, 99, 97]
measurement2 = [102, 117]

# Calculate difference between elements
list(imap(operator.sub, measurement1, measurement2))
# Out: [-2, -6]
list(imap(operator.sub, measurement2, measurement1))
# Out: [2, 6]

The mapping stops as soon as one iterable stops:

import operator

measurement1 = [100, 111, 99, 97]
measurement2 = [102, 117]

# Calculate difference between elements
list(map(operator.sub, measurement1, measurement2))
# Out: [-2, -6]
list(map(operator.sub, measurement2, measurement1))
# Out: [2, 6]

Found a mistake? Have a question or improvement idea? Let me know.

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