这是使用numpy.repeat和itertools.chain的一种方法.从概念上讲，这正是您想要做的:重复某些值，链接其他值.建议用于少量列，否则基于stack的方法可能会更好.

Here's one way using numpy.repeat and itertools.chain. Conceptually, this is exactly what you want to do: repeat some values, chain others. Recommended for small numbers of columns, otherwise stack based methods may fare better.

import numpy as np
from itertools import chain

# return list from series of comma-separated strings
def chainer(s):
    return list(chain.from_iterable(s.str.split(',')))

# calculate lengths of splits
lens = df['package'].str.split(',').map(len)

# create new dataframe, repeating or chaining as appropriate
res = pd.DataFrame({'order_id': np.repeat(df['order_id'], lens),
                    'order_date': np.repeat(df['order_date'], lens),
                    'package': chainer(df['package']),
                    'package_code': chainer(df['package_code'])})

print(res)

   order_id order_date package package_code
0         1  20/5/2018      p1         #111
0         1  20/5/2018      p2         #222
0         1  20/5/2018      p3         #333
1         3  22/5/2018      p4         #444
2         7  23/5/2018      p5         #555
2         7  23/5/2018      p6         #666