Pythonic Programming Tips for Software Engineers/

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Miscellaneous Tips

Miscellaneous Tips

Learn how to use sum(), pickle, and input() functions.

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sum() almost anything

The built-in sum() function is an excellent tool for summing up all numbers in an iterable and for operations dependent on such summation. For example, we can easily calculate the mean of a set, even if we don’t have access to statistics, numpy, scipy, or a similar module:

Python 3.8
data = {1, 1, 1, 1, 2, 3} # set() eliminates duplicates 
mean = sum(data) / len(data)
print(mean)

In fact, sum() is an optimized accumulator loop like this:

Python 3.8
def sum(iterable, init=0):
  for x in iterable:
    init += x 
  return init
print(sum([2,4,6,8]))

A notable exception

There is one notable exception. That is, sum() doesn’t allow us to concatenate a collection of strings. Concatenating a large list of strings is prohibitively inefficient. It is inefficient to the extent that Python developers invoked two rarely combined principles from The Zen of Python:

  1. Special cases aren’t special enough to break the rules (so, let sum() concatenate strings).
  2. Practicality beats purity.

We should avoid a list and tuple summation with ...