根据python另一列中的公共值在数据框的一列中划分2个值

Question

I have a dataframe, providing snippet of it:

Year       Result       Count
2000        lost          5
2000        won          16
2001        lost         12
2001        won          22
2002        lost         15
2002        won          15
2003        lost         12
2003        tied          1
2003        won          13
2004        lost          8
2004        won          20

I want to create a list of year wise win/loss ratio. I know how to to do it using dictionary and loop. But what is the best way to do it.

Answer 1

Here are two options:

Option 1 : pivot + division , use pivot to create separate columns for won , tie and lost and then divide the won column by the lost column:

df.pivot("Year", "Result", "Count").pipe(lambda x: x.won/x.lost)

#Year
#2000    3.200000
#2001    1.833333
#2002    1.000000
#2003    1.083333
#2004    2.500000
#dtype: float64

Option 2 : groupby + agg , group data frame by Year , and for each year divide the Count value of won by lost :

df.Count = df.Count.astype(float)
(df.set_index('Result').groupby('Year').Count
   .agg(lambda x: x.get('won', np.nan)/x.get('lost', np.nan)))

#Year
#2000    3.200000
#2001    1.833333
#2002    1.000000
#2003    1.083333
#2004    2.500000
#Name: Count, dtype: float64