Django PDB

Make debugging Django easier

Adding pdb.set_trace() to your source files every time you want to break into pdb sucks.

Don't do that.

Do this.

Installation

Install using pip:

pip install django-pdb

Add to your settings.py:

# Make sure to add django_pdb AFTER any apps that override the 'runserver'
# or 'test' commands (includes south and django.contrib.staticfiles)
INSTALLED_APPS = (
    ...
    'django_pdb',
    ...
)

# Make sure to add PdbMiddleware after all other middleware.
# PdbMiddleware only activates when settings.DEBUG is True.
MIDDLEWARE_CLASSES = (
    ...
    'django_pdb.middleware.PdbMiddleware',
)

Usage

manage.py runserver

Drops into pdb at the start of a view if the URL includes a pdb GET parameter.

Drops into ipdb at the start of a view if the URL includes a ipdb GET parameter.

This behavior is only enabled if settings.DEBUG = True:

bash: testproject/manage.py runserver
Validating models...

0 errors found
Django version 1.3, using settings 'testproject.settings'
Development server is running at http://127.0.0.1:8000/
Quit the server with CONTROL-C.

GET /test?pdb
function "myview" in testapp/views.py:7
args: ()
kwargs: {}

> /Users/tom/github/django-pdb/testproject/testapp/views.py(8)myview()
-> a = 1
(Pdb)

manage.py runserver --pdb or manage.py runserver --ipdb

Drops into pdb/ipdb at the start of every view:

bash: testproject/manage.py runserver --pdb
Validating models...

0 errors found
Django version 1.3, using settings 'testproject.settings'
Development server is running at http://127.0.0.1:8000/
Quit the server with CONTROL-C.

GET /test
function "myview" in testapp/views.py:7
args: ()
kwargs: {}

> /Users/tom/github/django-pdb/testproject/testapp/views.py(7)myview()
-> a = 1
(Pdb)

manage.py test --pdb or manage.py test --ipdb

Drops into pdb/ipdb on test errors/failures:

bash: testproject/manage.py test testapp --pdb
Creating test database for alias 'default'...
E
======================================================================
>>> test_error (testapp.tests.SimpleTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/tom/github/django-pdb/testproject/testapp/tests.py", line 16, in test_error
    one_plus_one = four
NameError: global name 'four' is not defined
======================================================================

> /Users/tom/github/django-pdb/testproject/testapp/tests.py(16)test_error()
-> one_plus_one = four
(Pdb)

Post mortem mode

manage.py runserver --pm

Post mortem mode, drops into (i)pdb if an exception is raised in a view. This works only if there is no other app overriding runserver command.

POST_MORTEM = True

You can also add `POST_MORTEM = True` to your `settings.py` to enable this option even if other app overrides `runserver`.

Filter

You can also use the template filter pdb or ipdb to explore a template variable in (i)pdb this way:

{% load pdb %}

{{ variable|pdb }}
{{ variable|ipdb }}
{{ variable|ipdb|a_filter_to_debug }}

Example:

bash: testproject/manage.py runserver
Validating models...

0 errors found
Django version 1.4, using settings 'testproject.settings'
Development server is running at http://127.0.0.1:8000/
Quit the server with CONTROL-C.
> /Users/tom/github/django-pdb/django_pdb/templatetags/pdb_filters.py(14)pdb()
-> return element
(Pdb) element
"I'm the variable"
(Pdb) element = "another value"
(Pdb) c
[11/May/2012 11:22:53] "GET /filter/ HTTP/1.1" 200 37

This is useful to inspect a complex object that isn't behaving as expected or debug a filter.

Other apps that override test/runserver

manage.py test --pdb works if you also have other apps that override the test command, as long as they use Python's unittest framework.

Make sure to put django_pdb after any conflicting apps in INSTALLED_APPS so that they have priority.