根据Pandas数据帧中其他列的值设置列的值

Question

I have this Pandas dataframe:

This is some fictional data about games of cricket played between two countries. I want to set the value of column winner based on this simple logic:

if country_1_runs == country_2_runs:
    winner = 3
elif country_1_runs > country_2_runs:
    winner = 1
else:
    winner = 2

I know about map and apply methods in Pandas. But I'm not certain if they allow conditional expressions like the above.

Answer 1

Use numpy.select :

m1 = df.country_1_runs == df.country_2_runs
m2 = df.country_1_runs > df.country_2_runs

df['winner'] = np.select([m1, m2], [3, 1], default=2)

Answer 2

You can try

df['winner'] = np.where(df['country_1_runs'] == df['country_2_runs'], 3, 
    np.where(df['country_1_runs']> df['country_2_runs'], 1, 2))