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pythonjsonfor-loop
Dmytro
Dmytro

Reputation: 355

Python, delete JSON element having specific key from a loop

Using Python, I need to delete all objects in JSON array that have specific value of 'name' key. However, I can't do that from a loop.

Imaging I want to delete all items having 'bad' as name in the following input:

{
  'myArray' : [
    {
      'name' : 'good',
      'value' : '1'
    },
    {
      'name' : 'bad',
      'value' : '2'
    }
  ]
}

So I use the following Python test case:

myData = {'myArray': [{'name': 'good', 'value': '1'}, {'name': 'bad', 'value': '2'}]}

for a in myData['myArray']:
  if (a['name'] =='bad'):
    del a

print(json.dumps(myData))

And I see that the myData is not changed.

I assume this is because I try to delete an iterator of a loop, that might be considered as risky action by interpreter, however no runtime error or warning is reported by Python.

What's the recommended approach in this case?

Thanks!

Upvotes: 6

Views: 13146

Answers (4)

Dmytro
Dmytro

Reputation: 355

One of approaches from Remove element from list when using enumerate() in python - a loop over a copy of the list referred as [:] - works too:

for a in myData['myArray'][:]:
  if (a['name'] == u'bad'):
     myData['myArray'].remove(a)

Thanks everyone!

Upvotes: 4

smci
smci

Reputation: 33970

Use a (nested) dict/list comprehension. Never try to delete elements of an object while iterating over it

>>> [x for x in myData['myArray'] if x['name'] != 'bad']
[{'name': 'good', 'value': '1'}]

Assign the result to myData['myArray'], or whatever you want.

Upvotes: 1

Pedro
Pedro

Reputation: 383

myData = {'myArray': [{'name': 'good', 'value': '1'}, {'name': 'bad', 'value': '2'}]}

myData_clean = [x for x in myData['myArray'] if x['name'] !='bad']
myData_clean = {'myArray':myData_clean}
print(myData_clean)

output:

{'myArray': [{'name': 'good', 'value': '1'}]}

Upvotes: 0

PARMESH
PARMESH

Reputation: 98

You can use the list comprehension. Below is the reference.

new_list =  [obj for obj in myData['myArray'] if(obj['name'] != 'bad')] 
print new_list

Upvotes: 0

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