一个月一个月

如果NaN真的为空

df.assign(**{
    'Start station': df['Start station'].fillna(df['End station'])})

    Duration      End station                         Start station
14      1407              NaN                        14th & V St NW
19       509              NaN                        21st & I St NW
20       638  15th & P St NW.                       15th & P St NW.
27      1532              NaN  Massachusetts Ave & Dupont Circle NW
28       759              NaN           Adams Mill & Columbia Rd NW

mask

如果NaN是字符串

df.assign(**{
    'Start station': df['Start station'].mask(
        lambda x: x == 'NaN', df['End station'])})

    Duration      End station                         Start station
14      1407              NaN                        14th & V St NW
19       509              NaN                        21st & I St NW
20       638  15th & P St NW.                       15th & P St NW.
27      1532              NaN  Massachusetts Ave & Dupont Circle NW
28       759              NaN           Adams Mill & Columbia Rd NW

使用combine_first。将列1中的空值替换为col2

df["station"] = df["End station"].combine_first(df["Start station"])
df.drop(["End station", "Start station"], 1, inplace=True)

>>> df
   Duration      End station                         Start station
0      1407              NaN                        14th & V St NW
1       509              NaN                        21st & I St NW
2       638  15th & P St NW.                                   NaN
3      1532              NaN  Massachusetts Ave & Dupont Circle NW
4       759              NaN           Adams Mill & Columbia Rd NW

为这两列指定相同的名称

>>> df.columns = df.columns.str.replace('.*?station', 'station')
>>> df
   Duration          station                               station
0      1407              NaN                        14th & V St NW
1       509              NaN                        21st & I St NW
2       638  15th & P St NW.                                   NaN
3      1532              NaN  Massachusetts Ave & Dupont Circle NW
4       759              NaN           Adams Mill & Columbia Rd NW

堆叠，然后拆堆。

>>> s = df.stack()
>>> s
0  Duration                                    1407
   station                           14th & V St NW
1  Duration                                     509
   station                           21st & I St NW
2  Duration                                     638
   station                          15th & P St NW.
3  Duration                                    1532
   station     Massachusetts Ave & Dupont Circle NW
4  Duration                                     759
   station              Adams Mill & Columbia Rd NW
dtype: object
>>> df = s.unstack()
>>> df
  Duration                               station
0     1407                        14th & V St NW
1      509                        21st & I St NW
2      638                       15th & P St NW.
3     1532  Massachusetts Ave & Dupont Circle NW
4      759           Adams Mill & Columbia Rd NW
>>>

这就是我的想法：
.stack创建了一个带有MultiIndex的序列，并为您处理空值。它在列名上对齐第二层，因为列名相同，所以只有一个列名-拆分只生成一个列。
如果不更改列名，这实际上只是根据索引之间的差异进行的猜测。

>>> # without changing column names
>>> s.index
MultiIndex(levels=[[0, 1, 2, 3, 4], ['Duration', 'End station', 'Start station']],
           labels=[[0, 0, 1, 1, 2, 2, 3, 3, 4, 4], [0, 2, 0, 2, 0, 1, 0, 2, 0, 2]])

>>> # column names the same
>>> s.index
MultiIndex(levels=[[0, 1, 2, 3, 4], ['Duration', 'station']],
           labels=[[0, 0, 1, 1, 2, 2, 3, 3, 4, 4], [0, 1, 0, 1, 0, 1, 0, 1, 0, 1]])

似乎有点棘手，也许有人会评论它。
替代方法-使用pd.concat和.dropna

>>> stations = pd.concat([df.iloc[:,1],df.iloc[:,2]]).dropna()
>>> stations.name = 'stations'
>>> stations
2                         15th & P St NW.
0                          14th & V St NW
1                          21st & I St NW
3    Massachusetts Ave & Dupont Circle NW
4             Adams Mill & Columbia Rd NW
Name: stations, dtype: object

>>> df2 = pd.concat([df['Duration'], stations], axis=1)
>>> df2
   Duration                              stations
0      1407                        14th & V St NW
1       509                        21st & I St NW
2       638                       15th & P St NW.
3      1532  Massachusetts Ave & Dupont Circle NW
4       759           Adams Mill & Columbia Rd NW

使用ffill

df.iloc[:,2:4]=df.iloc[:,2:4].ffill(1)