debug-with-emacs.xhtml [plain text]
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<title>Debugging Python(Twisted) with Emacs</title>
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<h1>Debugging Python(Twisted) with Emacs</h1>
<img src="http://yellow5.com/pokey/archive/pokey411_3.gif"/>
<span class="footnote">POKEY THE PENGUIN IS COPYRIGHT © 1998-2002
THE AUTHORS</span>
<ul>
<li>Open up your project files. sometimes emacs can't find them if you
don't have them open before-hand.</li>
<li> <code>M-x pdb</code>, Run pdb as: <code>twistd -b -f my.tap</code></li>
<li>while pdb waits for your input, go to a place in your code and hit
<code>C-x SPC</code> to insert a break-point. pdb should say something happy.
Do this in as many points as you wish.</li>
<li>Go to your pdb buffer and hit <code>c</code>; this runs as normal until a
break-point is found.</li>
<li>once you get to a breakpoint, use <code>s</code> to step, <code>n</code> to run the
current line without stepping through the functions it calls, <code>w</code>
to print out the current stack, <code>u</code> and <code>d</code> to go up and down a
level in the stack, <code>p foo</code> to print result of expression <code>foo</code>.</li>
<li>recommendations for effective debugging:
<ul>
<li>use <code>p self</code> a lot; just knowing the class where the current code
is isn't enough most of the time.</li>
<li>use <code>w</code> to get your bearings, it'll re-display the current-line/arrow</li>
<li>after you use <code>w</code>, use <code>u</code> and <code>d</code> and lots more <code>p self</code> on the
different stack-levels.</li>
<li>If you've got a big code-path that you need to grok, keep another
buffer open and list the code-path there (e.g., I had a
nasty-evil Deferred recursion, and this helped me tons)</li>
</ul>
</li>
</ul>
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