Calculate percentage of all alliances in year in dataframe pandas

Question

I have the dataframe that looks like (real frame has years from 1990 to 2020):

Year	Chains_Normalize	Alliance_Name
1990	0.000	Gaint Inc
1990	0.000	Kell Inc
1990	0.000	New Corp
1991	13.222	Sad Corp
1991	18.152	Second Corp
1991	16.333	Shin Inc
1992	19.212	No inc
1992	0.000	Third inc
1992	14.332	Fourth inc

I have to calculate the percentage of alliances in every year if Chains_Normalize is not 0. (The idea is to count what percentage of all alliances from dataframe includes every year)

The result will look like this:

Year  Percentage
1990  0.000
1991  33.333
1992  22.222

1990 has all zero alliances and it's percentage is 0.

1991 has 3 no-zero alliances and (3/9)*100 = 33.333

1992 has 2 no-zero alliances and (2/9)*100 = 22.222

Answer 1

Simply count the non-zeros per year and then divide by the length of df and multiply by 100 (which you already do manually with (N/9)*100 ):

>>> df['Chains_Normalize'].ne(0).groupby(df['Year']).sum() / len(df) * 100
Year
1990     0.000000
1991    33.333333
1992    22.222222
Name: Chains_Normalize, dtype: float64

this works because df['Chains_Normalize'].ne(0) returns a series of booleans where the alliances are non-zero, that you can then sum:

>>> df['Chains_Normalize'].ne(0)
0    False
1    False
2    False
3     True
4     True
5     True
6     True
7    False
8     True
Name: Chains_Normalize, dtype: bool