pandas, multiply all the numeric values in the data frame by a constant

Question

How to multiply all the numeric values in the data frame by a constant without having to specify column names explicitly? Example:

In [13]: df = pd.DataFrame         


        

Answer 1

One way would be to get the dtypes, match them against object and datetime dtypes and exclude them with a mask, like so -

df.ix[:,~np.in1d(df.dtypes,['object','datetime'])] *= 3

Sample run -

In [273]: df
Out[273]: 
  col1  col2  col3
0    A     1    30
1    B     2    10
2    C     3    20

In [274]: df.ix[:,~np.in1d(df.dtypes,['object','datetime'])] *= 3

In [275]: df
Out[275]: 
  col1  col2  col3
0    A     3    90
1    B     6    30
2    C     9    60