如何根据Python中的两个条件更改列的值

Question

我有一个数据集,我在游戏中有时间和事件的时间.

  EVENT     GAME
  0:34      0:43
  NaN       0:23
  2:34      3:43
  NaN       4:50

我想将GAME <0.24的EVENT列中的NaN替换为GAME列中的值.

 df['EVENT'][(df['GAME'] < '0:24') & (df['EVENT'] == 'NaN')] = df['GAME']

我试过这个但它不起作用.对不起,如果很明显.我是Python的新手.

Answer 1

你可以isnull用来检查NaN:

df.loc[(df['GAME'] < '0:24') & (df['EVENT'].isnull()), 'EVENT'] = df['GAME']
print (df)

  EVENT  GAME
0  0:34  0:43
1  0:23  0:23
2  2:34  3:43
3   NaN  4:50

另一个解决方案mask:

mask = (df['GAME'] < '0:24') & (df['EVENT'].isnull())
df['EVENT'] = df['EVENT'].mask(mask, df['GAME'])
print (df)
  EVENT  GAME
0  0:34  0:43
1  0:23  0:23
2  2:34  3:43
3   NaN  4:50

或者numpy.where:

df['EVENT'] = np.where(mask, df['GAME'], df['EVENT'])
print (df)
  EVENT  GAME
0  0:34  0:43
1  0:23  0:23
2  2:34  3:43
3   NaN  4:50