This came up in discussion here before, maybe a year ago, I think. There
was a decision not to change the implementation, but that seemed like a
mistake (and the discussion was about broader things).
Anyway, I propose that the obviously broken version of
`statistics.median()` be replaced with a better implementation.
Python 3.8.0 (default, Nov 6 2019, 21:49:08)
>>> import numpy as np
>>> import pandas as pd
>>> import statistics
>>> nan = float('nan')
>>> items1 = [nan, 1, 2, 3, 4]
>>> items2 = [1, 2, 3, 4, nan]
>>> statistics.median(items1)
2
>>> statistics.median(items2)
3
>>> np.median(items1)
nan
>>> np.median(items2)
nan
>>> pd.Series(items1).median()
2.5
>>> pd.Series(items2).median()
2.5
The NumPy and Pandas answers are both "reasonable" under slightly different
philosophies of how to handle bad values. I think raising an exception for
NaNs would also be reasonable enough.
The one thing that is NOT reasonable is returning different answers for
median depending on the order of the elements.
On Thu, Dec 26, 2019 at 10:10 AM Marco Sulla via Python-ideas <
python-ideas@python.org> wrote:
> So why only mean and not median, that's better for statistics? :D
>
> Seriously, if you want it builtin, add it to PYTHONSTARTUP:
> https://docs.python.org/3/using/cmdline.html#envvar-PYTHONSTARTUP
>
> from statistics import mean
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