understand pandas groupby/apply arguments group_keys and include_groups

understand pandas groupby apply arguments group_keys and include_groups.py

import pandas as pd

df = pd.DataFrame(
    {
        "A": ["foo", "bar", "foo", "bar", "foo", "bar", "foo", "foo"],
        "B": ["one", "one", "two", "three", "two", "two", "one", "three"],
        "C": np.random.randn(8),
        "D": np.random.randn(8),
    }
)
df.groupby('A', group_keys=True).apply(lambda x: x, include_groups=True) # group_keys matters when using apply
#          A      B         C         D
# A                                    
# bar 1  bar    one -1.583891 -1.708604
#     3  bar  three  0.352257 -0.088550
#     5  bar    two  0.857819 -0.480496
# foo 0  foo    one -0.290060  0.856008
#     2  foo    two  1.192185 -0.243608
#     4  foo    two  0.772302 -0.791737
#     6  foo    one -0.446585  1.177601
#     7  foo  three -1.776370  1.541010

df.groupby('A', group_keys=True).apply(lambda x: x, include_groups=False)
#            B         C         D
# A                               
# bar 1    one -1.583891 -1.708604
#     3  three  0.352257 -0.088550
#     5    two  0.857819 -0.480496
# foo 0    one -0.290060  0.856008
#     2    two  1.192185 -0.243608
#     4    two  0.772302 -0.791737
#     6    one -0.446585  1.177601
#     7  three -1.776370  1.541010

df.groupby('A', group_keys=False).apply(lambda x: x, include_groups=True)
#      A      B         C         D
# 0  foo    one -0.290060  0.856008
# 1  bar    one -1.583891 -1.708604
# 2  foo    two  1.192185 -0.243608
# 3  bar  three  0.352257 -0.088550
# 4  foo    two  0.772302 -0.791737
# 5  bar    two  0.857819 -0.480496
# 6  foo    one -0.446585  1.177601
# 7  foo  three -1.776370  1.541010

df.groupby('A', group_keys=False).apply(lambda x: x, include_groups=False)
#        B         C         D
# 0    one -0.290060  0.856008
# 1    one -1.583891 -1.708604
# 2    two  1.192185 -0.243608
# 3  three  0.352257 -0.088550
# 4    two  0.772302 -0.791737
# 5    two  0.857819 -0.480496
# 6    one -0.446585  1.177601
# 7  three -1.776370  1.541010