Collect common groups on non-index column across two dataframes

Question

Here are two dataframes grouped how I want them:

last5s = pd.Timestamp.now().replace(microsecond=0) - pd.Timedelta('5s')
dates = pd.date_range(last5s, periods = 5, freq='s')

N=10
data1 = np.random.randint(0,10,N)
data2 = np.random.randint(0,10,N)

df1 = pd.DataFrame({'timestamp': np.random.choice(dates, size=N), 'A': data1})
df2 = pd.DataFrame({'timestamp': np.random.choice(dates, size=N), 'B': data2})

print(df1)
print(df2)
print()

g1 = df1.groupby(pd.Grouper(key='timestamp', freq='1s'))
print("g1:")
for time, group in g1:
    print('time:', time)
    print(group)
    print()
    
print()
g2 = df2.groupby(pd.Grouper(key='timestamp', freq='1s'))
print('g2:')
for time, group in g2:
    print('time:', time)
    print(group)
    print()

Output (e.g.):

            timestamp  A
0 2024-03-01 10:05:26  7
1 2024-03-01 10:05:25  8
2 2024-03-01 10:05:28  1
3 2024-03-01 10:05:24  2
4 2024-03-01 10:05:28  5
5 2024-03-01 10:05:27  4
6 2024-03-01 10:05:24  6
7 2024-03-01 10:05:26  3
8 2024-03-01 10:05:26  8
9 2024-03-01 10:05:28  8
            timestamp  B
0 2024-03-01 10:05:25  1
1 2024-03-01 10:05:26  6
2 2024-03-01 10:05:25  5
3 2024-03-01 10:05:28  7
4 2024-03-01 10:05:27  7
5 2024-03-01 10:05:28  1
6 2024-03-01 10:05:28  4
7 2024-03-01 10:05:25  0
8 2024-03-01 10:05:24  6
9 2024-03-01 10:05:24  5

g1:
time: 2024-03-01 10:05:24
            timestamp  A
3 2024-03-01 10:05:24  2
6 2024-03-01 10:05:24  6

time: 2024-03-01 10:05:25
            timestamp  A
1 2024-03-01 10:05:25  8

time: 2024-03-01 10:05:26
            timestamp  A
0 2024-03-01 10:05:26  7
7 2024-03-01 10:05:26  3
8 2024-03-01 10:05:26  8

time: 2024-03-01 10:05:27
            timestamp  A
5 2024-03-01 10:05:27  4

time: 2024-03-01 10:05:28
            timestamp  A
2 2024-03-01 10:05:28  1
4 2024-03-01 10:05:28  5
9 2024-03-01 10:05:28  8


g2:
time: 2024-03-01 10:05:24
            timestamp  B
8 2024-03-01 10:05:24  6
9 2024-03-01 10:05:24  5

time: 2024-03-01 10:05:25
            timestamp  B
0 2024-03-01 10:05:25  1
2 2024-03-01 10:05:25  5
7 2024-03-01 10:05:25  0

time: 2024-03-01 10:05:26
            timestamp  B
1 2024-03-01 10:05:26  6

time: 2024-03-01 10:05:27
            timestamp  B
4 2024-03-01 10:05:27  7

time: 2024-03-01 10:05:28
            timestamp  B
3 2024-03-01 10:05:28  7
5 2024-03-01 10:05:28  1
6 2024-03-01 10:05:28  4

How do I "join" the groups together such that I can iterate over them together? E.g. I want to be able to do:

for time, group1, group2 in somehow_joined(g1,g2):
    <do stuff with group1 and group2 in this common time group>

Answer 1

You can just do:

for t, d1 in g1:
    d2 = g2.get_group(t)
    if d2 is None:
        print("I don't want this")
        continue

    print(d1)
    print('-'*10)
    print(d2)
    print('='*30)

Output:

            timestamp  A
0 2024-02-29 19:10:14  0
3 2024-02-29 19:10:14  7
7 2024-02-29 19:10:14  1
----------
            timestamp  B
1 2024-02-29 19:10:14  0
3 2024-02-29 19:10:14  6
5 2024-02-29 19:10:14  9
6 2024-02-29 19:10:14  4
==============================
            timestamp  A
2 2024-02-29 19:10:15  2
5 2024-02-29 19:10:15  8
6 2024-02-29 19:10:15  2
9 2024-02-29 19:10:15  6
----------
            timestamp  B
8 2024-02-29 19:10:15  9
==============================
            timestamp  A
1 2024-02-29 19:10:16  3
4 2024-02-29 19:10:16  9
8 2024-02-29 19:10:16  6
----------
            timestamp  B
2 2024-02-29 19:10:16  6
4 2024-02-29 19:10:16  6
==============================