Remove from dictionary seems to miss sometimes (python)-CodePudding

I have some json data in the following form:

data={'total': 5000, 'transactions': [{'info': foo, 'status': Success}, {'info': foo, 'status': Fail}]

I want to remove all the failures from the transactions, so I perform:

for txn in data['transactions']:
            if 'status' in txn:
                if txn['status'] == 'Fail':
                    data['transactions'].remove(txn)
                    data['total'] = data['total'] - 1
                    print('Fail 1 at: '   str(idx))

I believe this code works as it should (ie no errors and runs), but then I inspect the debugger and find failures still there. I even run this code immediately after:

for idx,txn in enumerate(data['transactions']):
     if 'status' in txn:
         if txn['status'] == 'Fail':
              print('Fail 2 at: ' str(idx))

Fail 2 returns less than Fail 1, but Fail 2 still returns more than zero. Am I missing something, like an incorrect removal here: data['transactions'].remove(txn) ?

See a small debug list of failures below:

Fail 1 at: 1
Fail 1 at: 81
Fail 1 at: 82
Fail 1 at: 105
Fail 1 at: 164

Fail 2 at: 82
Fail 2 at: 289
Fail 2 at: 353
Fail 2 at: 559
Fail 2 at: 573

CodePudding user response：

You're removing from the list while iterating. That can cause problems, as the memory is shifting while you're accessing it.

To resolve this issue, you can use filter():

data['transactions'] = list(filter(lambda x: x['status'] != 'Fail', data['transactions']))
print(data['transactions'])