Taking advantage of an enhanced interactive Python debugger with ipdb_Plone 3 Products Development Cookbook-QQ阅读男生都市网

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Taking advantage of an enhanced interactive Python debugger with ipdb

As a Python developer, you should already be familiar with pdb. So think of ipdb as a Python debugger with many of the advantages IPython provides. ipdb, for example, is much easier to use thanks to the IPython autocomplete feature.

Note

You can find the official documentation for pdb for Python 2.4 at http://www.python.org/doc/2.4.4/lib/module-pdb.html.

ipdb has another very useful and important feature which is the ability to get an IPython shell in our instance console whenever we want by means of adding the /ipdb suffix to any URL.

Note

ipdb is only available when Zope is running in the foreground mode.

How to do it…

Add the iw.debug line in eggs parameter of [buildout] part:

[buildout]

...

# Add additional eggs here 
eggs = 
 iw.debug

Insert an iw.debug line in the zcml parameter of [instance] part:

[instance]

...

# If you want to register ZCML slugs for any packages, 
# list them here. 
# e.g. zcml = my.package my.other.package 
zcml = 
 iw.debug

Rebuild your instance. We need to build our Zope instance again to let it know that there were some changes:
```
./bin/buildout
```
Run your instance. Then run the instance in foreground mode to get a handle of its console:
```
./bin/instance fg 
```

How it works…

Given that we haven't written any line of code yet, we won't call ipdb from inside the (non-existing) code. What we need to know is that by adding these lines anywhere in the code, we will get the prompt from the improved debugger:

import ipdb; ipdb.set_trace()

Note

If you leave any ipdb (or pdb) call in your code when running Zope in any but foreground mode, then you'll get a BdbQuit exception.

But we do have a Plone site running, so let's try to get an IPython shell on demand. Access http://localhost:8080/plone/ipdb and go to your foreground console.

There will be an ipdb prompt waiting for you. Use the ll command (double "L" in lowercase) to get a list of local variables. Then test some other things: context, is the object we called ipdb from, in our example, the Plone site. In this particular case, it also happens to be the portal variable.

Note

Don't forget to use Tab key to let ipdb auto-complete.

Note

More information about ipdb can be found at: http://pypi.python.org/pypi/iw.debug.