Query options in MongoDB

Introduction to MongoDB in Python

Filip Schouwenaars

Machine Learning Researcher

Limiting the number of results

from pymongo import MongoClient
client = MongoClient()
mov = client.film.movies


# Get all movies (cursor)
all_movies = mov.find()


# How many?
len(list(all_movies))

from pymongo import MongoClient
client = MongoClient()
mov = client.film.movies


# Get five movies (cursor)
limit_movies = mov.find().limit(5)


# How many?
len(list(limit_movies))

Sorting in ascending and descending order

# By title, ascending (A-Z)
t_sort = mov.find().sort("title", 1)
list(t_sort)

[
    {
        'title': '12 angry men',
        'release_year': 1957,
        ...
    },
    {
        'title': 'a beautiful mind',
        'release_year': 2001,
        ...
    },
    ...
]

# By release year, descending (high to low)
ry_sort = mov.find().sort("release_year", -1)
list(ry_sort)

[
    {
          'title': 'dune: part two',
        'release_year': 2024,
        ...
    },
     {
        'title': 'barbie',
        'release_year': 2023,
          ...
    },
    ...
]

Counting matching documents

from pymongo import MongoClient
client = MongoClient()
mov = client.film.movies


# Count action movies with find()
len(list(mov.find({ "genre": "action" })))

# Count action movies, but better
mov.count_documents({ "genre": "action" })

Using projection to shape your results

movies = mov.find({}, {
  "title": 1, "rating": 1,
})
list(movies)

[
 {'_id': '6...f', 'rating': 7.6, 'title': 'superbad'},
 {'_id': '6...0', 'rating': 8.6, 'title': 'interstellar'},
 {'_id': '6...1', 'rating': 8.8, 'title': 'inception'},
 {'_id': '6...2', 'rating': 9.2, 'title': 'the godfather'},
 {'_id': '6...3', 'rating': 8,   'title': 'the revenant'},
 ...
]

movies = mov.find({}, {
  "title": 1, "rating": 1, "_id": 0
})
list(movies)

[
 {'title': 'superbad', 'rating': 7.6},
 {'title': 'interstellar', 'rating': 8.6},
 {'title': 'inception', 'rating': 8.8},
 {'title': 'the godfather', 'rating': 9.2},
 {'title': 'the revenant', 'rating': 8},
 ...
]

Let's practice!

Introduction to MongoDB in Python