python - Counting unique values in a column in pandas dataframe like in Qlik? -


if have table this: 

df = pd.dataframe({          'hid': [101, 102, 103, 101, 102, 104, 105, 101],          'did': [10, 11, 12, 10, 11, 10, 12, 10],          'uid': ['james', 'henry', 'abe', 'james', 'henry', 'brian', 'claude', 'james'],          'mid': ['a', 'b', 'a', 'b', 'a', 'a', 'a', 'c'] })

i can count(distinct hid) in qlik come count of 5 unique hid. how do in python using pandas dataframe? or maybe numpy array? similarly, if count(hid) 8 in qlik. equivalent way in pandas?

count distict values, use nunique:

df['hid'].nunique() 5

count non-null values, use count: 

df['hid'].count() 8

count total values including null values, use size attribute: 

df['hid'].size 8

edit add condition

use boolean indexing:

df.loc[df['mid']=='a','hid'].agg(['nunique','count','size'])

or using query:

df.query('mid == "a"')['hid'].agg(['nunique','count','size'])

output:

nunique    5 count      5 size       5 name: hid, dtype: int64

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