Cross-join two pandas DataFrame

Say you have groups and subgroups, and you want to combine in a DataFrame all possible combinations of groups and subgroups.

# Import libraries
import pandas as pd
from IPython.display import display

# Create DataFrames
df_groups = pd.DataFrame({'group': ['A', 'B', 'C']})
display(df_groups)

df_subgroups = pd.DataFrame({'subgroup': list(range(5))})
display(df_subgroups)
group
0 A
1 B
2 C
subgroup
0 0
1 1
2 2
3 3
4 4

This can be done with a cross-join, using the merge() function with argument how='cross'.

# Combine DataFrames with a cross-join
df_groups.merge(df_subgroups, how='cross')
group subgroup
0 A 0
1 A 1
2 A 2
3 A 3
4 A 4
5 B 0
6 B 1
7 B 2
8 B 3
9 B 4
10 C 0
11 C 1
12 C 2
13 C 3
14 C 4