Pandas 用其他值替换一列值
Pandas replacing the one column value with other
示例数据如下：
Time,RangeGreen,RangeRed,DistanceGreenRed,SlopeGreen,SlopeRed,PreviousCandleColor,CurrentCandleColor
2018.04.02 00:01:01,30-40,20-30,14.42241040084485,0.002837507264410963,-0.002233901393132696,Green,indecisive
2018.04.02 00:03:06,40-50,30-40,9.228956001044772,3.969502900848433,7.203315124348411,Green,indecisive
2018.04.02 00:04:06,10-20,30-40,-13.69498672180752,-19.36590965829607,-2.850639197642629,Red,indecisive
我愿意用 PreviousCandleColor 替换 CurrentCandleColor 值，但是 CurrentCandleColor 的第 0 个值应该是 PreviousCandleColor 的第一个值。
因此我的最终值必须是：
Time,RangeGreen,RangeRed,DistanceGreenRed,SlopeGreen,SlopeRed,PreviousCandleColor,CurrentCandleColor
2018.04.02 00:01:01,30-40,20-30,14.42241040084485,0.002837507264410963,-0.002233901393132696,Green,Green
2018.04.02 00:03:06,40-50,30-40,9.228956001044772,3.969502900848433,7.203315124348411,Green,Red
2018.04.02 00:04:06,10-20,30-40,-13.69498672180752,-19.36590965829607,-2.850639197642629,Red,indecisive
我试过这样移动它；
df['CurrentCandleColor'] = df[1:'PreviousCandleColor']
但是我得到了以下错误：
TypeError: cannot do slice indexing on <class 'pandas.core.indexes.range.RangeIndex'> with these indexers [PreviousCandleColor] of <class 'str'>
请帮助我。
如果此处没有NaNs，则使用shift with fillna：
a = df.loc[df.index[-1], 'CurrentCandleColor']
df['CurrentCandleColor'] = df['PreviousCandleColor'].shift(-1).fillna(a)
print (df)
Time ... CurrentCandleColor
0 2018.04.02 00:01:01 ... Green
1 2018.04.02 00:03:06 ... Red
2 2018.04.02 00:04:06 ... indecisive
[3 rows x 8 columns]
或者：
df['CurrentCandleColor'] =df['PreviousCandleColor'].shift(-1).fillna(df['CurrentCandleColor'])
如果可能，NaNs 值首先获取列的最后一个值，然后返回：
last = df['CurrentCandleColor'].values[-1]
df['CurrentCandleColor'] = df['PreviousCandleColor'].shift(-1)
df.loc[df.index[-1], 'CurrentCandleColor'] = last
示例数据如下：
Time,RangeGreen,RangeRed,DistanceGreenRed,SlopeGreen,SlopeRed,PreviousCandleColor,CurrentCandleColor
2018.04.02 00:01:01,30-40,20-30,14.42241040084485,0.002837507264410963,-0.002233901393132696,Green,indecisive
2018.04.02 00:03:06,40-50,30-40,9.228956001044772,3.969502900848433,7.203315124348411,Green,indecisive
2018.04.02 00:04:06,10-20,30-40,-13.69498672180752,-19.36590965829607,-2.850639197642629,Red,indecisive
我愿意用 PreviousCandleColor 替换 CurrentCandleColor 值，但是 CurrentCandleColor 的第 0 个值应该是 PreviousCandleColor 的第一个值。
因此我的最终值必须是：
Time,RangeGreen,RangeRed,DistanceGreenRed,SlopeGreen,SlopeRed,PreviousCandleColor,CurrentCandleColor
2018.04.02 00:01:01,30-40,20-30,14.42241040084485,0.002837507264410963,-0.002233901393132696,Green,Green
2018.04.02 00:03:06,40-50,30-40,9.228956001044772,3.969502900848433,7.203315124348411,Green,Red
2018.04.02 00:04:06,10-20,30-40,-13.69498672180752,-19.36590965829607,-2.850639197642629,Red,indecisive
我试过这样移动它；
df['CurrentCandleColor'] = df[1:'PreviousCandleColor']
但是我得到了以下错误：
TypeError: cannot do slice indexing on <class 'pandas.core.indexes.range.RangeIndex'> with these indexers [PreviousCandleColor] of <class 'str'>
请帮助我。
如果此处没有NaNs，则使用shift with fillna：
a = df.loc[df.index[-1], 'CurrentCandleColor']
df['CurrentCandleColor'] = df['PreviousCandleColor'].shift(-1).fillna(a)
print (df)
Time ... CurrentCandleColor
0 2018.04.02 00:01:01 ... Green
1 2018.04.02 00:03:06 ... Red
2 2018.04.02 00:04:06 ... indecisive
[3 rows x 8 columns]
或者：
df['CurrentCandleColor'] =df['PreviousCandleColor'].shift(-1).fillna(df['CurrentCandleColor'])
如果可能，NaNs 值首先获取列的最后一个值，然后返回：
last = df['CurrentCandleColor'].values[-1]
df['CurrentCandleColor'] = df['PreviousCandleColor'].shift(-1)
df.loc[df.index[-1], 'CurrentCandleColor'] = last