To find documents based on top-level attributes, we can simply use a dictionary:

>>> books.find({"name": "Mastering MongoDB"})

[{u'_id': ObjectId('592149c4aabac953a3a1e31e'),
 u'isbn': u'101',
 u'name': u'Mastering MongoDB',
 u'price': 30.0,
 u'published': datetime.datetime(2017, 6, 25, 0, 0)}]

To find documents in an embedded document, we can use the dot notation. In the following example, we use meta.authors to access the authors embedded document inside the meta document:

>>> result = list(books.find({"meta.authors": {"$regex": "aLEx", "$options": "i"}}))
>>> pprint(result)

[{u'_id': ObjectId('593c24443c8ca55b969c4c54'),
 u'isbn': u'201',
 u'meta': {u'authors': u'alex giamas'},
 u'name': u'Mastering MongoDB, 2nd Edition'}]

In this example, we used a regular expression to match aLEx, case-insensitive, in every document in which the string is mentioned in the meta.authors embedded document. PyMongo uses this notation for regular expression queries, called the $regex notation in MongoDB documentation. The second parameter is the options parameter for $regex, which we'll explain in great detail in the Using regular expressions section later in this chapter.

Comparison operators are also supported, a full list of which is given in the Comparison operators section later in this chapter:

>>> result = list(books.find({ "price": {  "$gt":40 } }))
>>> pprint(result)

[{u'_id': ObjectId('594061a9aabac94b7c858d3d'),
 u'isbn': u'301',
 u'name': u'Python and MongoDB',
 u'price': 60}]

Adding multiple dictionaries in our query results in a logical AND query:

>>> result = list(books.find({"name": "Mastering MongoDB", "isbn": "101"}))
>>> pprint(result)

[{u'_id': ObjectId('592149c4aabac953a3a1e31e'),
 u'isbn': u'101',
 u'name': u'Mastering MongoDB',
 u'price': 30.0,
 u'published': datetime.datetime(2017, 6, 25, 0, 0)}]

For books having both isbn=101 and name=Mastering MongoDB, to use logical operators such as $or and $and we have to use this syntax:

>>> result = list(books.find({"$or": [{"isbn": "101"}, {"isbn": "102"}]}))
>>> pprint(result)

[{u'_id': ObjectId('592149c4aabac953a3a1e31e'),
 u'isbn': u'101',
 u'name': u'Mastering MongoDB',
 u'price': 30.0,
 u'published': datetime.datetime(2017, 6, 25, 0, 0)},
{u'_id': ObjectId('59214bc1aabac954263b24e0'),
 u'isbn': u'102',
 u'name': u'MongoDB in 7 years',
 u'price': 50.0,
 u'published': datetime.datetime(2017, 6, 26, 0, 0)}]

For books having an isbn of 101 or 102, if we want to combine AND and OR operators we have to use the $and operator like this:

>>> result = list(books.find({"$or": [{"$and": [{"name": "Mastering MongoDB", "isbn": "101"}]}, {"$and": [{"name": "MongoDB in 7 years", "isbn": "102"}]}]}))
>>> pprint(result)
[{u'_id': ObjectId('592149c4aabac953a3a1e31e'),
 u'isbn': u'101',
 u'name': u'Mastering MongoDB',
 u'price': 30.0,
 u'published': datetime.datetime(2017, 6, 25, 0, 0)},
{u'_id': ObjectId('59214bc1aabac954263b24e0'),
 u'isbn': u'102',
 u'name': u'MongoDB in 7 years',
 u'price': 50.0,
 u'published': datetime.datetime(2017, 6, 26, 0, 0)}]

For a result of OR between 2 queries.

• The first query is asking for documents that have isbn=101 AND name=Mastering MongoDB
• The second query is asking for documents that have isbn=102 AND name=MongoDB in 7 years
• The result is the union of these two datasets