Answers for "pandas count distinct"

pandas groupby column count distinct values

# Pandas group by a column looking at the count unique/count distinct values of another column

df.groupby('param')['group'].nunique()

pandas count distinct values in a column

Series.value_counts(self, normalize=False, sort=True, ascending=False, bins=None, dropna=True)

pandas count distinct values in column

#column name ISSDTM
pd.to_datetime(df.ISSDTM, errors='coerce').dt.year

#result
0    2013
1    2013
2    2009
3    2009
Name: ISSDTM, dtype: int64