dataframe count by column value code example

Example 1: pandas get count of column

df['column_name'].value_counts()

Example 2: pandas count values by column

df = pd.DataFrame({'a':list('abssbab')})
df.groupby('a').count()

Example 3: pandas count

>>> df.set_index(["Person", "Single"]).count(level="Person")
        Age
Person
John      2
Lewis     1
Myla      1

Example 4: python count variable and put the count in a column of data frame

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