Read Data from MongoDB

Specify a Query

Exact Match

results = collection.find({ "color": "yellow" })

Comparison Operators

• $gt: Greater than
• $lte: Less than or Equal
• $ne: Not equal

results = collection.find({ "rating": { "$gt" : 2 }})

Logical Operators

• $and, which returns all documents that match the conditions of all clauses
• $or, which returns all documents that match the conditions of one clause
• $nor, which returns all documents that do not match the conditions of any clause
• $not, which returns all documents that do not match the expression

results = collection.find({ 
    "$or": [
        { "qty": { "$gt": 5 }},
        { "color": "yellow" }
    ]
})

Array Operators

• $all, which returns documents with arrays that contain all elements in the query
• $elemMatch, which returns documents if an element in their array field matches all conditions in the query
• $size, which returns all documents with arrays of a specified size

results = collection.find({
    "type" : { "$size": 2 }
})

Element Operators

results = collection.find( { "color" : { "$exists": "true" }} )

Evaluation Operators

• $text, which performs a text search on the documents
• $regex, which returns documents that match a specified regular expression
• $mod, which performs a modulo operation on the value of a field and returns documents where the remainder is a specified value

results = collection.find({ "name" : { "$regex" : "p{2,}" }} )

Retrieve Data

restaurant = sample_restaurants.restaurants.find_one({"cuisine": "Bakery"})

cursor = sample_restaurants.restaurants.find({"cuisine": "Spanish"})

Specify Fields To Return

Specify Fields to Include

{ "<Field Name>": 1 }

results = restaurants.find({ "name" : "Emerald Pub"}, {"name": 1, "cuisine": 1, "borough": 1})

Exclude the _id Field

results = restaurants.find({ "name" : "Emerald Pub"}, {"_id": 0, "name": 1, "cuisine": 1, "borough": 1})

Specify Fields to Exclude

{ "<Field Name>": 0 }

Specify Documents to Return

results = restaurants.find({ "cuisine" : "Italian"}) \
                     .sort("name", pymongo.ASCENDING) \
                     .limit(5) \
                     .skip(10)

备注

The order in which you call these methods doesn't change the documents that are returned. The driver automatically reorders the calls to perform the sort and skip operations first, and the limit operation afterward

Count Documents

collection.count_documents({ "author": "Mike" })

Retrieve Distinct Field Values

results = restaurants.distinct("borough")

results = restaurants.distinct("borough", {
    "cuisine": "Italian"
})

Access Data From a Cursor

results = collection.find()

for document in results:
    print(document)

print(results.next())

all_results = list(results)

results.close()