find, lt and gt Examples (MongoDB)Use the MongoDB find method with lt and gt queries to find ranges of documents.
Find, MongoDB. A real estate database might have a price for each house. We want to find just properties that have a field within a range of values (like a certain price).
With special range queries, used with the find() method, we can find documents with fields in a certain range. The $lt and $gt terms are useful here.
A program. Here we have a real estate database with 3 houses in it. Each house has a different price. We use find() to get matching houses with prices less than, or greater than, a value.
Detail We use the string "$lt" in a nested dictionary argument to find a range of prices less than a value.
Detail The "$gt" operator works the same way as less than, but means greater than.
from pymongo import MongoClient client = MongoClient("mongodb://") db = client.real_estate # Reset. db.houses.delete_many({}) # Insert houses. db.houses.insert_many([ {"address": "100 Main St.", "price": 45000}, {"address": "110 Main St.", "price": 50000}, {"address": "1400 Rich Ave.", "price": 200000}, ]) # Find inexpensive houses. print("FIND PRICE LT 60000") cursor = db.houses.find({"price": {"$lt": 60000}}) for doc in cursor: print(doc) # Find expensive houses. print("FIND PRICE GT 60000") cursor = db.houses.find({"price": {"$gt": 60000}}) for doc in cursor: print(doc)
FIND PRICE LT 60000 {'address': '100 Main St.', '_id': ObjectId('59f122302514972194e7e975'), 'price': 45000} {'address': '110 Main St.', '_id': ObjectId('59f122302514972194e7e976'), 'price': 50000} FIND PRICE GT 60000 {'address': '1400 Rich Ave.', '_id': ObjectId('59f122302514972194e7e977'), 'price': 200000}
Notes, comparison operators. For small groups of documents, getting all documents and then checking them in an if-statement in Python is possible.
However For large amounts of data, this because impossible. Using MongoDB to query for ranges (with lt and gt) is faster.
A review. Find() can be used with ranges. A dictionary argument with a special term (lt or gt) enables a range query. For large databases, this is essential.
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