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Question

I've got an involved situation. Let's say I have the following example dataframe of loans:

test_df = pd.DataFrame({'name': ['Jack','Jill','John','Jack','Jill'],
                   'date': ['2016-08-08','2016-08-08','2016-08-07','2016-08-08','2016-08-08'],
                   'amount': [1000.0,1500.0,2000.0,2000.0,3000.0],
                   'return_amount': [5000.0,2000.0,3000.0,0.0,0.0],
                   'return_date': ['2017-08-08','2017-08-08','2017-08-07','','2017-08-08']})

test_df.head()

    amount  date        name    return_amount   return_date
0   1000.0  2016-08-08  Jack    5000.0          2017-08-08
1   1500.0  2016-08-08  Jill    2000.0          2017-08-08
2   2000.0  2016-08-07  John    3000.0          2017-08-07
3   2500.0  2016-08-08  Jack    0.0
4   2500.0  2016-08-08  Jill    0.0             2017-08-08

There are a few operations I need to perform after grouping this dataframe by name (grouping loans by person):

1) return amount needs to allocated proportionally by the sum of amount .

2) If return date is missing for ANY loan for a given person, then all return_dates should be converted to empty strings ''.

I already have a function that I use to allocate the proportional return amount:

def allocate_return_amount(group):
    loan_amount = group['amount']
    return_amount = group['return_amount']
    sum_amount = loan_amount.sum()
    sum_return_amount = return_amount.sum()
    group['allocated_return_amount'] = (loan_amount/sum_amount) * sum_return_amount
    return group

And I use grouped_test_df = grouped_test_df.apply(allocate_return_amount) to apply it.

What I am struggling with is the second operation I need to perform, checking if any of the loans to a person are missing a return_date , and if so, changing all return_dates for that person to ''.

I've found GroupBy.all in the pandas documentation , but I haven't figured out how to use it yet, anyone with experience with this?

Since this example might be a bit hard to follow, here's my ideal output for this example:

ideal_test_df.head()

    amount  date        name    return_amount   return_date
0   1000.0  2016-08-08  Jack    0.0             ''
1   1500.0  2016-08-08  Jill    666.66          2017-08-08
2   2000.0  2016-08-07  John    3000.0          2017-08-07
3   2500.0  2016-08-08  Jack    0.0             ''
4   2500.0  2016-08-08  Jill    1333.33         2017-08-08

Hopefully this makes sense, and thank you in advance to any pandas expert who takes the time to help me out!

Answer 1

You can do it by iterating through the groups, testing the condition using any , then setting back to the original dataframe using loc :

test_df = pd.DataFrame({'name': ['Jack','Jill','John','Jack','Jill'],
                   'date': ['2016-08-08','2016-08-08','2016-08-07','2016-08-08','2016-08-08'],
                   'amount': [1000.0,1500.0,2000.0,2000.0,3000.0],
                   'return_amount': [5000.0,2000.0,3000.0,0.0,0.0],
                   'return_date': ['2017-08-08','2017-08-08','2017-08-07','','2017-08-08']})

grouped = test_df.groupby('name')

for name, group in grouped:
    if any(group['return_date'] == ''):
        test_df.loc[group.index,'return_date'] = ''

And if you want to reset return_amount also, and don't mind the additional overhead, just add this line right after:

test_df.loc[group.index, 'return_amount'] = 0