Python’s date.strftime() slower than str(), split, unpack, and concatenate?

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I was surprised to find that date.strftime() is slower than converting the date to a string, splitting the string into a list, unpacking the list into year, month, and day strings and then concatenating those to format the date:

def date_to_str(date):
    year, month, day = str(date).split('-')
    return month + '/' + day + '/' + day

Here’s the full test, using IPython’s magic %timeit command:

import datetime
def date_to_str(date):
    year, month, day = str(date).split('-')
    return month + '/' + day + '/' + day
today =
%timeit date_to_str(today)
%timeit today.strftime('%m/%d/%Y')

And the results:

1000000 loops, best of 3: 1.82 µs per loop
100000 loops, best of 3: 6 µs per loop

The date_to_str() function runs about 3 times faster than date.strftime(). Strange. But, again, we’re talking about nanoseconds.

Written by Nat Dunn.

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