python - Pandas 按月计算计数

Question

如何用fill统计每个月的项目数？

data = [
        {"event_date": "2018-08-10", "tags": ["tv", "radio"]},
        {"event_date": "2018-08-11", "tags": ["tv", "radio"]},
        {"event_date": "2018-09-10", "tags": ["tv"]},
        {"event_date": "2018-11-10", "tags": ["tv", "wifi"]}
    ] 
df = pd.DataFrame(data)
df.groupby([(df['event_date']).dt.month, df['tags']]).count()

我的期望:

month tv radio wifi
8 2 2 0
9 1 0 0
10 0 0 0
11 1 0 1

Answer 1

所以这是 unnest ,get_dummies 和reindex 混合题

df.event_date=pd.to_datetime(df.event_date).dt.month

l=list(range(df.event_date.min(),df.event_date.max()+1))
df.set_index('event_date').tags.apply(pd.Series).stack().\
  str.get_dummies().sum(level=0).\
   reindex(l,fill_value=0)
Out[834]: 
            radio  tv  wifi
event_date                 
8               2   2     0
9               0   1     0
10              0   0     0
11              0   1     1