Best Way to Calculate Column Percentage of Total Pandas

Question

Say I have the following dataframe:

>>> df=pd.DataFrame([[150,90,60],[200,190,10],[400,150,250]], columns=['Total','Group1','Group2'])
>>> df
   Total  Group1  Group2
0    150      90      60
1    200     190      10
2    400     150     250
>>> 

As you can see, Group 1 and Group 2 sum up to the Total (think age categories in Census Data). I want to calculate the percentage within each group.

Right now I'm doing this as follows:

>>> df2=df.copy()
>>> for Group in ['Group1','Group2']:
...     df2[Group]=df[Group]/df['Total']*100
... 
>>> 
>>> df2
   Total  Group1  Group2
0    150    60.0    40.0
1    200    95.0     5.0
2    400    37.5    62.5
>>> 

However, I'm sure there is a way to do this without the for loop. Perhaps using applymap or map? Can someone show me the more efficient way to do this calculation?

Answer 1

You can just divide as follows:

>>> df.div(df.Total.values, axis=0)
   Total  Group1  Group2
0      1   0.600   0.400
1      1   0.950   0.050
2      1   0.375   0.625

I wouldn't recommend mixing values and percentages, but if you really want to, you can reassign Total :

df2 = df.div(df.Total.values, axis=0)
df2['Total'] = df.Total

Answer 2

>>> print df.drop('Total', axis=1).divide(df.Total, axis=0)
   Group1  Group2
0   0.600   0.400
1   0.950   0.050