Get Median by Group in pandas DataFrame Column in Python (2 Examples)

This article shows how to calculate the median value by group in the Python programming language.

Preparing the Examples

import pandas as pd                                # Load pandas library
my_df = pd.DataFrame({'A':range(19, 28),           # Constructing a pandas DataFrame
                      'B':[6, 7, 3, 9, 1, 3, 8, 8, 9],
                      'C':range(20, 11, - 1),
                      'GRP_a':['gr1', 'gr1', 'gr2', 'gr3', 'gr1', 'gr2', 'gr2', 'gr3', 'gr3'],
                      'GRP_b':['a', 'b', 'c', 'c', 'a', 'b', 'b', 'a', 'a']})
print(my_df)
#     A  B   C GRP_a GRP_b
# 0  19  6  20   gr1     a
# 1  20  7  19   gr1     b
# 2  21  3  18   gr2     c
# 3  22  9  17   gr3     c
# 4  23  1  16   gr1     a
# 5  24  3  15   gr2     b
# 6  25  8  14   gr2     b
# 7  26  8  13   gr3     a
# 8  27  9  12   gr3     a

Example 1: Calculating Median by Group in Python

print(my_df.groupby('GRP_a').median())             # Computing the column median by group
#         A  B   C
# GRP_a           
# gr1    20  6  19
# gr2    24  3  15
# gr3    26  9  13

Example 2: Calculating Median by Group & Subgroup in Python

print(my_df.groupby(['GRP_a', 'GRP_b']).median())  # Computing the column median by multiple groups
#                 A    B     C
# GRP_a GRP_b                 
# gr1   a      21.0  3.5  18.0
#       b      20.0  7.0  19.0
# gr2   b      24.5  5.5  14.5
#       c      21.0  3.0  18.0
# gr3   a      26.5  8.5  12.5
#       c      22.0  9.0  17.0

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