PyMongoArrow

1.13.0 verified Mon Apr 27 auth: no python

PyMongoArrow bridges MongoDB with NumPy, Pandas, Polars, and PyArrow. Version 1.13.0 adds parallel batch processing and Polars ExtensionTypes support. Released ~monthly.

pip install pymongoarrow

Common errors

error ImportError: cannot import name 'patch_all' from 'pymongoarrow' ↓

cause Import path changed in older versions; patch_all is in pymongoarrow.monkey.

fix

Use: from pymongoarrow.monkey import patch_all

error TypeError: 'Schema' object is not callable ↓

cause Schema is not a function; it's a class that takes keyword arguments.

fix

Use: Schema({'field': type}) instead of Schema('field', type)

error pymongo.errors.OperationFailure: unknown command: aggregation ↓

cause MongoDB server version too old (<3.6) or missing aggregation support.

fix

Upgrade MongoDB to >=3.6 or use a different query method.

Warnings

breaking In v1.11.0, Python 3.9 support was dropped and Python 3.13 free-threaded was dropped on some platforms. The TypeRegistry in write() now extends rather than replaces. ↓

fix Upgrade to Python >=3.10. If writing Arrow data, do not expect old TypeRegistry replacement behavior.

deprecated PyMongoArrow 1.13.0 is still using pymongo.monkey.patch_all() which may change in future versions. ↓

fix Monitor release notes for deprecation; consider using API directly with Schema and find_arrow_all.

gotcha Schema inference may overflow for large integers (e.g., int64) if not explicitly defined. In v1.13.0, schema inference raises OverflowError for out-of-range values. ↓

fix Always define Schema explicitly for fields that may exceed inferred type range.

gotcha pandas is an optional dependency; if not installed, find_pandas_all() will raise ImportError. ↓

fix Install pymongoarrow[pandas] or pandas separately.

Install

pip install pymongoarrow[polars]

pip install pymongoarrow[pandas]

pip install pymongoarrow[all]

Imports

pymongoarrow
```
import pymongoarrow
```
pymongoarrow.api
```
from pymongoarrow.api import Schema
```

Quickstart

Basic usage: patch pymongo, define schema, query collections to get Arrow/Pandas/Polars outputs.

import os
import pymongo
from pymongoarrow.api import Schema
from pymongoarrow.monkey import patch_all

# Patch pymongo to enable arrow operations
patch_all()

client = pymongo.MongoClient(os.environ.get('MONGODB_URI', 'mongodb://localhost:27017'))
db = client.test
coll = db.mydata

# Define schema (field name: type)
schema = Schema({'name': str, 'age': int, 'city': str})

# Insert sample data
coll.insert_many([
    {'name': 'Alice', 'age': 30, 'city': 'NYC'},
    {'name': 'Bob', 'age': 25, 'city': 'SF'},
])

# Fetch as Arrow table
import pyarrow as pa
table = coll.find_arrow_all({}, schema=schema)
print(table)

# Convert to pandas
df = coll.find_pandas_all({}, schema=schema)
print(df)

# Convert to polars
import polars as pl
pl_df = coll.find_polars_all({}, schema=schema)
print(pl_df)