按日期合并CSV条目并按日期计数条目

最简单的是添加由 DataFrame.assign 和 Series.value_counts :

df = df.groupby('date').sum().assign(counts=df['date'].value_counts())
print (df)
            mentions  photos  replies  retweets  likes  polarity  counts
date                                                                    
2011-04-01         1       2       15         8     30      -0.2       2
2011-04-02         5       1       17         7    155       0.9       3
2011-04-03         1       1        1         2      2       0.2       1

dict.fromkeys 按所有列 date -可能用于骨料 size rename 它:

d = dict.fromkeys(df.columns.difference(['date']), 'sum')
d['date'] = 'size'
df = df.groupby('date').agg(d).rename(columns={'date':'counts'})
print (df)
            likes  mentions  photos  polarity  replies  retweets  counts
date                                                                    
2011-04-01     30         1       2      -0.2       15         8       2
2011-04-02    155         5       1       0.9       17         7       3
2011-04-03      2         1       1       0.2        1         2       1

细节

print (d)
{'likes': 'sum', 'mentions': 'sum', 'photos': 'sum', 'polarity': 'sum', 
 'replies': 'sum', 'retweets': 'sum', 'date': 'size'}