Pymongo: How to query MongoDB for existing and non-empty string field?

Question

This is a great answer to the question "how to query for an existing and non-null field". But I also need to check that a field is not an empty string. So the complete query needs to check that:

field exists
field is not NULL
field is not an empty string.

What's the best way to do that?

Dennis Golomazov · Accepted Answer · 2018-06-19 17:46:15Z

5

Use {'$nin': [None, '']}:

col.insert({})
col.insert({'test_field': None})
col.insert({'test_field': ''})
col.insert({'test_field': 'value'})

list(col.find({'test_field': {'$exists': True}}))
 [{u'_id': ObjectId('5b293fa7b5b55217c9afe7d0'), u'test_field': None},
  {u'_id': ObjectId('5b293fb1b5b55217c9afe7d2'), u'test_field': u''},
  {u'_id': ObjectId('5b293fb6b5b55217c9afe7d3'), u'test_field': u'value'}]

list(col.find({'test_field': {'$ne': None}}))
 [{u'_id': ObjectId('5b293fb1b5b55217c9afe7d2'), u'test_field': u''},
  {u'_id': ObjectId('5b293fb6b5b55217c9afe7d3'), u'test_field': u'value'}]

list(col.find({'test_field': {'$nin': [None, '']}}))
 [{u'_id': ObjectId('5b293fb6b5b55217c9afe7d3'), u'test_field': u'value'}]

answered Jun 19, 2018 at 17:46

Dennis Golomazov

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