1.6.7 Debugging Code

If you are using the web.error module from a command line or supporting webserver such as scripts/webserver.py in the source directory you can raise a web.error.Breakpoint Exception and it will be caught and provide a prompt from which you can debug your code.

#!/usr/bin/env python

# show python where the modules are
import sys; sys.path.append('../'); sys.path.append('../../../') 

import web.error; web.error.handle('debug')

print "Setting value to 5"
value = 5
print "Raising a Breakpoint so you can inspect value"
raise web.error.Breakpoint
print "The program has exited so this will not be printed"

This code provides a prompt that can be used as follows:

> python "command-web-error-debug.py"
Setting value to 5
Raising a Breakpoint so you can inspect value
> y:\doc\src\lib\command-web-error-debug.py(11)?()
-> raise web.error.Breakpoint
(Pdb) value
5
(Pdb) exit

The prompt uses the pdb module. To exit the debugger type exit and press Return. Code after the web.error.Breakpoint Exception was raised is not executed.