python - pandas - 计算列中值的使用

Question

我正在尝试计算不同用户使用某个值的次数。这是一个例子。

import pandas as pd
user = ['1', '2', '3', '1']
val = [['a','b','c'],['a'],['c','d'],['a','d']]
df = pd.DataFrame({'user': user, 'val': val})

user    val
 1      [a, b, c]
 2      [a]
 3      [c, d]
 1      [a, d]

我的预期输出如下:

val     count
 a      2
 b      1
 c      2
 d      2

Answer 1

您可以使用collections.Counter:

import pandas as pd
from collections import Counter
from itertools import chain
user = ['1', '2', '3', '1']
val = [['a','b','c'],['a'],['c','d'],['a','d']]
df = pd.DataFrame({'user': user, 'val': val})

pd.Series(Counter(chain.from_iterable(df.groupby("user").val.apply(lambda s:set(chain.from_iterable(s))))))