python count values in dataframe code example

Example 1: count values pandas

>>> index = pd.Index([3, 1, 2, 3, 4, np.nan])
>>> index.value_counts()
3.0    2
4.0    1
2.0    1
1.0    1
dtype: int64

Example 2: python count variable and put the count in a column of data frame

df['freq'] = df.groupby('myvar')['myvar'].transform('count')