将函数应用于pandas数据框中的所有其他列

Question

I have the below code which rounds every column in my dataframe:

def column_round(decimals):
    return partial(pd.Series.round, decimals=decimals)

df = df.apply(column_round(2))

I'd like to do this to every other column, in a new dataframe that I have. I believe i read somewhere that :: is a built in notation for stepping, but i'm not quite sure how to use it.

Answer 1

You can do:

df[df.columns[::2]].apply(column_round(2))

This steps over the df columns so you can sub-select them

Example:

In [2]:
df = pd.DataFrame(columns=list('abcdefgh'))
df

Out[2]:
Empty DataFrame
Columns: [a, b, c, d, e, f, g, h]
Index: []

In [3]:
df.columns[::2]

Out[3]:
Index(['a', 'c', 'e', 'g'], dtype='object')