python: pandas:根据条件将其他数据框中的值添加到新列中

Question

我有两个数据框，其中包含以下数据:

fixtures = pd.DataFrame(
{'HomeTeam': ["A", "B", "C", "D"], 'AwayTeam': ["E", "F", "G", "H"]})
ratings = pd.DataFrame({'team': ["A", "B", "C", "D", "E", "F", "G", "H"], "rating": [
"1,5", "0,2", "0,5", "2", "3", "4,8", "0,9", "-0,4"]})

现在我想将ratings["rating"]的值映射到各自的团队名称，但我无法让它工作。是否有可能有新的列与评级出现在HomeTeam和AwayTeam列的右侧?

预期输出:

设备:

homeTeam  homeTeamRating  awayTeam  AwayTeamRating  
Team A    1,5             Team E    3

Answer 1

可以使用:

to_replace=dict(zip(ratings.team,ratings.rating)) #create a dict. Key is team name value is rating.
#{'A': '1,5', 'B': '0,2', 'C': '0,5', 'D': '2', 'E': '3', 'F': '4,8', 'G': '0,9', 'H': '-0,4'}
fixtures['homeTeamRating']=fixtures['HomeTeam'].map(to_replace) #use map and  replace team column as a new column.
fixtures['AwayTeamRating']=fixtures['AwayTeam'].map(to_replace)
fixtures=fixtures[['HomeTeam','homeTeamRating','AwayTeam','AwayTeamRating']]
'''
HomeTeam homeTeamRating AwayTeam AwayTeamRating
0        A            1,5        E              3
1        B            0,2        F            4,8
2        C            0,5        G            0,9
3        D              2        H           -0,4
'''

Answer 2

如果您需要在现有列上应用一个方法来计算一些值，这些值最终将作为新列添加到现有的DataFrame中，那么pandas.DataFrame.apply()方法应该可以做到这一点。