Python Tutorial

Python MongoDB - Insert

Add one document or many, and read back the generated _id.

Insert One Document

Pass a dictionary to insert_one. MongoDB adds a unique _id automatically if you do not supply one.

from pymongo import MongoClient

client = MongoClient("mongodb://localhost:27017/")
customers = client["mydatabase"]["customers"]

doc = {"name": "John", "address": "Highway 37"}
result = customers.insert_one(doc)

print(result.inserted_id)      # e.g. ObjectId('652f...')

The _id Field

Every document has a unique _id. By default it is an ObjectId — a 12-byte value that also encodes its creation time. You may set your own _id instead (it must be unique).

customers.insert_one({"_id": 1, "name": "Amy"})   # custom id
# inserting another {"_id": 1} raises DuplicateKeyError

Insert Many Documents

insert_many takes a list of dictionaries and returns all generated ids in order.

people = [
    {"name": "Amy",   "address": "Apple st 652"},
    {"name": "Hannah","address": "Mountain 21"},
    {"name": "Michael","address": "Valley 345"},
]
result = customers.insert_many(people)
print(result.inserted_ids)     # list of ObjectIds

Documents Can Have Different Fields

Because collections are schema-less, documents need not match. This flexibility is a core MongoDB feature.

customers.insert_many([
    {"name": "Ann"},                                  # no address
    {"name": "Ben", "address": "5th Ave", "vip": True},  # extra field
])

Ordered vs Unordered Inserts

By default insert_many stops at the first error. Set ordered=False to keep inserting the valid documents and collect errors at the end.

from pymongo.errors import BulkWriteError

try:
    customers.insert_many(docs, ordered=False)
except BulkWriteError as e:
    print("Some inserts failed:", e.details["writeErrors"])

Best Practices

  • Use insert_many for bulk writes — far faster than looping insert_one.
  • Let MongoDB generate _id unless you have a natural unique key.
  • Use ordered=False when partial success is acceptable.
  • Keep a consistent document shape even though it is not enforced.

Try It Yourself

Exercise 1: Insert three documents in a single call and print their ids.

Show solution
docs = [{"n": 1}, {"n": 2}, {"n": 3}]
result = coll.insert_many(docs)
print(result.inserted_ids)

Exercise 2: If you do not supply _id, what does MongoDB do?

Show solution

It generates a unique ObjectId automatically.

📘 Real-World Deep Dive

Knowing <strong>MongoDB Insert (MongoDB)</strong> well is what turns MongoDB from a curiosity into a daily tool — you'll reach for it in nearly every real project.

Real-Life Scenario

An end-to-end usage of MongoDB Insert that you'd actually see in a data pipeline or analytics notebook.

Real-Life Example

from pymongo import MongoClient
from datetime import datetime, timezone
db = MongoClient().demo
doc = {"sensor": "temp-01", "value": 22.4, "ts": datetime.now(timezone.utc)}
res = db.readings.insert_one(doc)
print("inserted id:", res.inserted_id)

Expected Output

(see source)

Common mistakes

  • Inserting a dict with embedded datetime works, but naive datetime (without UTC) leads to subtle comparison bugs.
  • Queries with type-mismatched values silently return no results — cast at the boundary or use bson codecs.
  • find() returns a cursor — call list(cursor) only once you intend to materialise results.
  • Treating MongoDB Insert as a black box without reading the docs — the API has subtle defaults that bite when you scale.

🚀 Performance & Best Practices

  • Project only the fields you need: collection.find({}, {"name": 1}).
  • Use bulk_write instead of looping over single inserts / updates — order-of-magnitude faster.
  • Create indexes: collection.create_index([("field", pymongo.ASCENDING)]).
  • When working with MongoDB, prefer vectorised / batched operations over Python loops.

🧪 Try It Yourself

  1. Reproduce the snippet on a representative slice of your own data.
  2. Profile the snippet with cProfile or timeit and find the single biggest improvement.
  3. Generalise the snippet into a small, reusable function you can drop into future projects.

FAQ: Python MongoDB - Insert

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What is Python MongoDB - Insert?

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This Python MongoDB - Insert tutorial shows python mongodb - insert syntax with short MongoDB examples. Use the code blocks in this lesson for the exact statements, then try them in your editor.

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