21.3. "cgitb" --- Traceback manager for CGI scripts
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**Source code:** Lib/cgitb.py

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The "cgitb" module provides a special exception handler for Python
scripts. (Its name is a bit misleading.  It was originally designed to
display extensive traceback information in HTML for CGI scripts.  It
was later generalized to also display this information in plain text.)
After this module is activated, if an uncaught exception occurs, a
detailed, formatted report will be displayed.  The report includes a
traceback showing excerpts of the source code for each level, as well
as the values of the arguments and local variables to currently
running functions, to help you debug the problem.  Optionally, you can
save this information to a file instead of sending it to the browser.

To enable this feature, simply add this to the top of your CGI script:

   import cgitb
   cgitb.enable()

The options to the "enable()" function control whether the report is
displayed in the browser and whether the report is logged to a file
for later analysis.

cgitb.enable(display=1, logdir=None, context=5, format="html")

   This function causes the "cgitb" module to take over the
   interpreter's default handling for exceptions by setting the value
   of "sys.excepthook".

   The optional argument *display* defaults to "1" and can be set to
   "0" to suppress sending the traceback to the browser. If the
   argument *logdir* is present, the traceback reports are written to
   files.  The value of *logdir* should be a directory where these
   files will be placed. The optional argument *context* is the number
   of lines of context to display around the current line of source
   code in the traceback; this defaults to "5". If the optional
   argument *format* is ""html"", the output is formatted as HTML.
   Any other value forces plain text output.  The default value is
   ""html"".

cgitb.handler(info=None)

   This function handles an exception using the default settings (that
   is, show a report in the browser, but don't log to a file). This
   can be used when you've caught an exception and want to report it
   using "cgitb".  The optional *info* argument should be a 3-tuple
   containing an exception type, exception value, and traceback
   object, exactly like the tuple returned by "sys.exc_info()".  If
   the *info* argument is not supplied, the current exception is
   obtained from "sys.exc_info()".
