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, which is case insensitive, in every document that 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 will explain in detail in the Using regular expressions section later in this chapter.

Comparison operators are also supported, and a full list of these are given in the Comparison operators section, which can be seen 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 the following 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, as follows:

>>> 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 two queries, consider the following:

• 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