python - Pandas:Find the repeating patterns in a column and group them as cycles

Question

I've a column with values 'loading', 'unloading','nan'. I want to look for the pattern of 'loading' and 'unloading' in that order and mark those corresponding rows as cycle1, cycle2 so on.

The pic shows one such sequence where 'loading' and 'unloading' and I want a new column to have the values of '1' for all those rows and the next sequence of 'loading' and 'unloading' as '2' so on.

I've got no logic to show you but would appreciate if you can help me. The below pic shows what I expect

Answer 1

Here's a loop based way to do it. I'd be excited if someone else has a way that better makes use of pandas.

import pandas as pd

data = {'Event': ['Start','Going','Stop','Start','Stop','Start','Start','Going','Going','Going','Stop','Stop','Start','Stop']}


df = pd.DataFrame(data)

cycle = 0            
new_cycle = True
cycles = []
for x in df.Event:
    if new_cycle and x == 'Start':
        new_cycle = False
        cycle += 1
    elif x == 'Stop':
        new_cycle = True
    cycles.append(cycle)

df['cycles'] = cycles
print(df)

Output

    Event  cycles
0   Start       1
1   Going       1
2    Stop       1
3   Start       2
4    Stop       2
5   Start       3
6   Start       3
7   Going       3
8   Going       3
9   Going       3
10   Stop       3
11   Stop       3
12  Start       4
13   Stop       4