python中有多少用户具有相同的字符串值出现

Question

我想知道有多少用户具有相同的字符串值 数据为python数据帧类型，值的顺序无关紧要，应该计数一次（x-y与y-x相同）

user_id    value
1            x
1            y   
2            x
2            y
2            z   
3            x
3            z

Combination   #of user
x-y             2
x-z             2
y-z             1

Answer 1

按组创建组合，然后将值chain.from_iterable展平，然后将Counter计数：

from  itertools import combinations, chain
from collections import Counter

s = df.groupby('user_id')['value'].apply(lambda x: list(map( '-'.join, combinations(x, 2))))
#if necessary sorted combinations
#s = (df.groupby('user_id')['value']
#       .apply(lambda x: ['-'.join(sorted(y)) for y in combinations(x, 2)]))

d = Counter(chain.from_iterable(s))

df = pd.DataFrame({'Combination': list(d.keys()),
                   'user':list(d.values())})
print (df)
  Combination  user
0         x-y     2
1         x-z     2
2         y-z     1