34 items tagged “debugging”
2024
snoop. Neat Python debugging utility by Alex Hall: snoop lets you “import snoop” and then add “@snoop” as a decorator to any function, which causes that function’s source code to be output directly to the console with details of any variable state changes that occur while it’s running.
I didn’t know you could make a Python module callable like that—turns out it’s running “sys.modules[’snoop’] = snoop” in the __init__.py module!
2021
Finding and reporting an asyncio bug in Python 3.10
I found a bug in Python 3.10 today! Some notes on how I found it and my process for handling it once I figured out what was going on.
[... 1,789 words]2018
github-debug.com (via) This is a neat trick: GitHub have a dedicated site for their support engineers to send you to if you can’t connect to them. The site tests download speeds from their various domains and then lets you click a button to have GitHub run a traceroute/ping from their servers to your detected IP address and output the results (use devtools to spy on their API method for doing this). Then you can paste the results into a message to their support team. Turns out fastly-debug.com and dropbox-debug.com implement a similar pattern for those services as well.
Just switched to
{window.localStorage.getItem('debug') && <pre>{JSON.stringify(this.state, null, 2)}</pre>}- now I can ship to production and turn on debugging in my console withlocalStorage.setItem('debug', 1)
— @simonw
2010
Appending the request URL to SQL statements in Django. A clever frame-walking monkey-patch which pulls the most recent HttpRequest object out of the Python stack and adds the current request.path to each SQL query as an SQL comment, so you can see it in debugging tools such as slow query logs and the PostgreSQL “select * from pg_stat_activity” query.
Fun with TextMate and PDB. TextMate bookmarks (against lines in a file) are stored as OS X extended attributes, which can be accessed from Python using the xattr module. Here’s a clever piece of code that uses bookmarks to set breakpoints in the command-line pdb debugger.
Presenting django-devserver, a better runserver. I really like this—it’s a Django management command (./manage.py rundevserver) which adds SQL logging and cache access summaries to the console output of Django’s local development server. It solves a similar set of problems to the debug toolbar, but requires slightly less setup and doesn’t inject additional HTML in to your pages. You can add your own custom modules to it as well.
2009
Debugging in Python. The missing manual for Python’s powerful pdb debugger.
Deep Tracing of Internet Explorer. dynaTrace Ajax looks like an awesome tool. For once, Internet Explorer has a development tool that other browsers can be jealous of.
django-debug-toolbar. The new panel styling for the Django debug toolbar is really slick—here’s a neatly produced screencast demonstrating it (with Gypsy Jazz accompaniment).
Debugging Django in Production Revisited. Eric Holscher expands his show-technical-errors-to-superusers middleware to only show them to users in the group named “Technical Errors”.
Why I don’t love JavaScript’s Module Pattern. Jonathan Snook points out that the module pattern (where private functionality is hidden in a closure and only public methods are revealed to outside scopes) makes code a lot harder to debug. I use the module pattern for pretty much everything, not because I want to keep stuff private but more to avoid any chance of leaking out in to the global namespace. If I need to debug a value I temporarily assign it as a property on the global window object.
Finding and fixing memory leaks in Python. Using Dozer, a clever piece of WSGI middleware which displays sparklines of Python object counts and allows you to introspect them, using the gc module under the hood.
Announcing django-viewtools. A really excellent idea—run ./manage.py viewtools --pdb /path/on/site/ to debug a view in your Django project that is raising an error using the Python debugger, or use --profile to run the full request cycle for that URL through the profiler.
2008
ReferenceError: console is not defined. Since Firebug 1.2 you need to call window.loadFirebugConsole() in order for console.log and friends to work.
Introducing the Django Debug Toolbar. Another project inspired by DjangoCon: a component based debugging toolbar for Django. I like the architecture so far.
Django snippets: server with debugging backdoor. Six lines of code that uses spawning to fire up a Django server on port 8000 and a remote interactive interpreter backdoor on port 8001, so you can interogate the state of your server within the same process.
Super User Conditional Page Exception Reporting. The name is almost as long as the code snippet: this serves Django’s debug page to logged in super-users, falling back to the default 500 template for everyone else.
Firebug Lite 1.2 (via) Huge upgrade to the IE/Opera/Safari bookmarklet version of Firebug—it now has DOM element inspection, XHR tracking and an interactive console, among other features.
Debugging Django, a slidecast. I used SlideShare’s slidecast tool for the first time to synchronize audio of my Django London User Group talk with the slides. The talk included several live demos which aren’t represented in the slides so it’s a bit piecemeal in places.
modswgi: Debugging Techniques. mod_wsgi is excellent software, and the documentation is equally superb. I used these instructions recently to run the Python debugger inside a running instance of Apache, which helped my track down some import errors that weren’t occurring with Django’s development server.
Debugging Django
I gave a talk on Debugging Django applications at Monday’s inaugural meeting of DJUGL, the London Django Users Group. I wanted to talk about something that wasn’t particularly well documented elsewhere, so I pitched the talk as “Bug Driven Development”—what happens when Test Driven Development goes the way of this unfortunate pony.
The slides [... 1,759 words]Firebug Command Line API. Another thing I didn’t know about Firebug: you can set a breakpoint at the start of a function with “debug(fn)” and log all calls to it with “monitor(fn)”.
Opera Dragonfly. Opera’s new Firebug-style developer console. Out in alpha and it shows (slow to load and the interactive console leaves a lot to be desired) but still looks incredibly promising, especially the remote debugging tools for working with Opera on phones and games consoles.
Advanced JavaScript Debugging Techniques. There’s more to JavaScript debugging than just Firebug.
Firebug + Dijit tips. News to me: Firebug has a magic $1 variable which corresponds to the currently selected node. Very handy.
2007
I don't even use Firefox and Firebug anymore, the revised Web Inspector in Leopard has been incorporated in Coda and that does everything I need and more.
DebugBar. Suggested at BarCamp London 3 as a useful tool for developing with IE; apparently includes a great JavaScript debugger.
jQuery Logging (via) Brilliant four line jQuery plugin that lets you insert Firebug console.log() calls directly in to chains.
XRAY now works in IE. Westciv’s smart CSS debugging bookmarklet now works in IE 6.