CODEWITHSUNDEEP
pythonpython-2.7
Anonypy
Anonypy

Reputation: 73

Difference between these two formulas

For calculating the mean/average;

sum(j) / len(j)
sum(j) / max(len(j), 1)

I came across the second one earlier, but as far as I can tell, they do identical things. Can anyone explain the difference, if any?

Upvotes: 0

Views: 57

Answers (1)

Didrik Galteland
Didrik Galteland

Reputation: 228

The last expression is used in order to avoid dividing by 0. By assuming j is a list, if the array is empty, you will get a 0/0 expression if len(j) is used on it's own which will lead to an ZeroDivisionError.

>>> j = []
>>> sum(j) / len(j)
ZeroDivisionErrorTraceback (most recent call last)
<ipython-input-119-2bf5531faf2b> in <module>()
----> 1 sum(j) / len(j)

ZeroDivisionError: division by zero

The max(len(j),1) will ensure that the divisor never will be 0 and no error raised:

>>> sum(j) / max(len(j), 1)
0.0

Upvotes: 3

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