pandas get column average/mean

I can't get the average or mean of a column in pandas. A have a dataframe. Neither of things I tried below gives me the average of the column weight

    >>> allDF 
             ID           birthyear  weight
    0        619040       1962       0.1231231
    1        600161       1963       0.981742
    2      25602033       1963       1.3123124     
    3        624870       1987       0.94212

The following returns several values, not one:

    allDF[['weight']].mean(axis=1)

So does this:

    allDF.groupby('weight').mean()

If you only want the mean of the weight column, select the column (which is a Series) and call .mean():

    In [479]: df
    Out[479]: 
             ID  birthyear    weight
    0    619040       1962  0.123123
    1    600161       1963  0.981742
    2  25602033       1963  1.312312
    3    624870       1987  0.942120

    In [480]: df["weight"].mean()
    Out[480]: 0.83982437500000007

From: stackoverflow.com/q/31037298

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