Pyramid Transaction Manager

2.6 · active · verified Wed Apr 15

pyramid_tm is a package that integrates the Python `transaction` package with the Pyramid web framework, allowing Pyramid requests to join the active transaction. It provides centralized transaction management for Pyramid applications without relying on external WSGI middleware. Maintained by the Pylons Project, it has a generally active release cadence, with version 2.6 released in November 2024.

Warnings

breaking Version 2.6 dropped support for Python 3.7 and 3.8. Ensure your environment uses Python 3.9 or newer.
Fix: Upgrade your Python environment to 3.9 or later, or use an older `pyramid-tm` version compatible with your Python runtime.
breaking The behavior of the `tm.commit_veto` hook changed in version 2.2. It will now be consulted for squashed exceptions (exceptions handled by an exception view) instead of always aborting. It inspects `request.exception` and the response to determine whether to commit or abort.
Fix: Review and update any custom `tm.commit_veto` implementations to account for the new behavior regarding squashed exceptions.
gotcha Accessing `request.tm` outside the `pyramid_tm` tween or during a request where `pyramid_tm` was explicitly disabled (e.g., via an activate hook or `tm.active` in WSGI environ for testing) will raise an `AttributeError`.
Fix: Ensure `request.tm` is only accessed within the context where the `pyramid_tm` tween is active. For testing, set `tm.active` in the WSGI environ to `False` to disable it, or `tm.manager` to provide your own transaction manager.
gotcha If you manually complete a transaction using `request.tm.abort()` or `request.tm.commit()`, subsequent uses of the transaction manager within the same request will fail unless `request.tm.begin()` is explicitly invoked again to start a new transaction.
Fix: After explicit `abort()` or `commit()`, call `request.tm.begin()` if further transaction-managed operations are required within the same request cycle.
gotcha If `repoze.tm` or `repoze.tm2` middleware is present in the WSGI pipeline, `pyramid_tm` becomes inactive. These middlewares handle transaction management themselves and conflict with `pyramid_tm`.
Fix: Remove `repoze.tm` or `repoze.tm2` from your WSGI pipeline if you intend to use `pyramid_tm` for transaction management.

Install

pip install pyramid-tm Install `pyramid-tm`

Imports

pyramid_tm
```
config.include('pyramid_tm')
```
Include the package in your Pyramid application's configuration.

Quickstart

This minimal Pyramid application demonstrates how to include `pyramid_tm`. Once included, any operations involving data managers (like ZODB or SQLAlchemy with `zope.sqlalchemy`) will automatically join the transaction associated with the request.

from wsgiref.simple_server import make_server
from pyramid.config import Configurator
from pyramid.response import Response

def hello_world(request):
    # Any database operations here would automatically join the active transaction
    return Response('Hello World from pyramid_tm!')

if __name__ == '__main__':
    with Configurator() as config:
        config.include('pyramid_tm') # Enable pyramid_tm
        config.add_route('hello', '/')
        config.add_view(hello_world, route_name='hello')
        app = config.make_wsgi_app()
    server = make_server('0.0.0.0', 6543, app)
    print("Pyramid server running on http://0.0.0.0:6543")
    server.serve_forever()

view raw JSON →