Cross-join two pandas DataFrames

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