pandas getattr(df, "mean") doesn't work like df.mean()

Question

When I use getattr() to dynamically access the mean of a pandas dataframe or series, it returns a Series.mean object. However, when I use df.mean() to access the mean, it returns a float.

Why doesn't getattr() return the same thing that the normal method does?

Minimal reproducible code:

import pandas as pd
import numpy as np

s = pd.Series(np.random.randn(5))
print(getattr(s, "mean"))
>>> <bound method Series.mean of 
>>> 0    1.158042
>>> 1   -0.586821
>>> 2   -1.976764
>>> 3    1.722072
>>> 4    1.129570
print(s.mean())
>>> dtype: float64>
>>> 0.28921963496328584

I have used dir(getattr(s, "mean")) to attempt to get the mean value, but can't figure out which attribute, if any, will get me the float mean value.

The returned attribute is a callable. So call it, by post pending a `()` — Stephen Rauch, Dec 31 '17 at 02:16
brilliant. I did not realize that `getattr` returns the method attribute unless it is appended with parentheses. I was only familiar with `getattr` usage of type attributes. If you add an answer, @SahilDahiya, I will happily accept it. — conchoecia, Dec 31 '17 at 02:18

score 6 · Accepted Answer · answered Dec 31 '17 at 02:23

6

Since returned atttribute by getattr is callable, try:

print(getattr(s, "mean")())

answered Dec 31 '17 at 02:23

Sahil Dahiya

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pandas getattr(df, "mean") doesn't work like df.mean()

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