===================================
cgitb -- Detailed traceback reports
===================================
.. module:: cgitb
:synopsis: Mis-named module that provides extended traceback information.
:Purpose: cgitb provides more detailed traceback information than :mod:`traceback`.
:Python Version: 2.2 and later
:mod:`cgitb` was originally designed for showing errors and debugging
information in web applications. It was later updated to include
plain-text output as well, but unfortunately wasn't renamed. This has
led to obscurity and the module is not used as often as it should be.
Nonetheless, :mod:`cgitb` is a valuable debugging tool in the standard
library.
Standard Traceback Dumps
========================
Python's default exception handling behavior is to print a *traceback*
to standard error with the call stack leading up to the error
position. This basic output frequently contains enough information to
understand the cause of the exception and permit a fix.
.. include:: cgitb_basic_traceback.py
:literal:
:start-after: #end_pymotw_header
The above sample program has a subtle error in :func:`func3()`.
.. {{{cog
.. cog.out(run_script(cog.inFile, 'cgitb_basic_traceback.py', ignore_error=True))
.. }}}
::
$ python cgitb_basic_traceback.py
Traceback (most recent call last):
File "cgitb_basic_traceback.py", line 22, in <module>
func1(1)
File "cgitb_basic_traceback.py", line 12, in func1
return func2(local_var)
File "cgitb_basic_traceback.py", line 16, in func2
return func3(local_var)
File "cgitb_basic_traceback.py", line 19, in func3
local_var = arg2 / 2
NameError: global name 'arg2' is not defined
.. {{{end}}}
Enabling Detailed Tracebacks
============================
While the basic traceback includes enough information for us to spot
the error, enabling cgitb replaces ``sys.excepthook`` with a function
that gives extended tracebacks with even more detail.
.. include:: cgitb_extended_traceback.py
:literal:
:start-after: #end_pymotw_header
As you can see below, the error report is much more extensive. Each
frame of the stack is listed, along with:
* the full path to the source file, instead of just the base name
* the values of the arguments to each function in the stack
* a few lines of source context from around the line in the error path
* the values of variables in the expression causing the error
.. {{{cog
.. cog.out(run_script(cog.inFile, 'cgitb_extended_traceback.py', ignore_error=True))
.. }}}
::
$ python cgitb_extended_traceback.py
<type 'exceptions.NameError'>
Python 2.7: /Users/dhellmann/.virtualenvs/pymotw/bin/python
Sun Oct 24 08:53:18 2010
A problem occurred in a Python script. Here is the sequence of
function calls leading up to the error, in the order they occurred.
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_extended_traceback.py in <module>()
21 def func3(arg3):
22 local_var = arg2 / 2
23 return local_var
24
25 func1(1)
func1 = <function func1>
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_extended_traceback.py in func1(arg1=1)
13 def func1(arg1):
14 local_var = arg1 * 2
15 return func2(local_var)
16
17 def func2(arg2):
global func2 = <function func2>
local_var = 2
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_extended_traceback.py in func2(arg2=2)
17 def func2(arg2):
18 local_var = arg2 + 2
19 return func3(local_var)
20
21 def func3(arg3):
global func3 = <function func3>
local_var = 4
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_extended_traceback.py in func3(arg3=4)
20
21 def func3(arg3):
22 local_var = arg2 / 2
23 return local_var
24
local_var undefined
arg2 undefined
<type 'exceptions.NameError'>: global name 'arg2' is not defined
__class__ = <type 'exceptions.NameError'>
__delattr__ = <method-wrapper '__delattr__' of exceptions.NameError object>
__dict__ = {}
__doc__ = 'Name not found globally.'
__format__ = <built-in method __format__ of exceptions.NameError object>
__getattribute__ = <method-wrapper '__getattribute__' of exceptions.NameError object>
__getitem__ = <method-wrapper '__getitem__' of exceptions.NameError object>
__getslice__ = <method-wrapper '__getslice__' of exceptions.NameError object>
__hash__ = <method-wrapper '__hash__' of exceptions.NameError object>
__init__ = <method-wrapper '__init__' of exceptions.NameError object>
__new__ = <built-in method __new__ of type object>
__reduce__ = <built-in method __reduce__ of exceptions.NameError object>
__reduce_ex__ = <built-in method __reduce_ex__ of exceptions.NameError object>
__repr__ = <method-wrapper '__repr__' of exceptions.NameError object>
__setattr__ = <method-wrapper '__setattr__' of exceptions.NameError object>
__setstate__ = <built-in method __setstate__ of exceptions.NameError object>
__sizeof__ = <built-in method __sizeof__ of exceptions.NameError object>
__str__ = <method-wrapper '__str__' of exceptions.NameError object>
__subclasshook__ = <built-in method __subclasshook__ of type object>
__unicode__ = <built-in method __unicode__ of exceptions.NameError object>
args = ("global name 'arg2' is not defined",)
message = "global name 'arg2' is not defined"
The above is a description of an error in a Python program. Here is
the original traceback:
Traceback (most recent call last):
File "cgitb_extended_traceback.py", line 25, in <module>
func1(1)
File "cgitb_extended_traceback.py", line 15, in func1
return func2(local_var)
File "cgitb_extended_traceback.py", line 19, in func2
return func3(local_var)
File "cgitb_extended_traceback.py", line 22, in func3
local_var = arg2 / 2
NameError: global name 'arg2' is not defined
.. {{{end}}}
The end of the output also includes the full details of the exception
object (in case it has attributes other than ``message`` that would be
useful for debugging) and the original form of a traceback dump.
Local Variables in Tracebacks
=============================
Having access to the variables involved in the error stack can help
find a logical error that occurs somewhere higher in the stack than
the line where the actual exception is generated.
.. include:: cgitb_local_vars.py
:literal:
:start-after: #end_pymotw_header
In the case of this code with a :ref:`ZeroDivisionError
<exceptions-ZeroDivisionError>`, we can see that the problem is
introduced in the computation of the value of ``c`` in ``func1()``,
rather than where the value is used in ``func2()``.
.. {{{cog
.. cog.out(run_script(cog.inFile, 'cgitb_local_vars.py', ignore_error=True))
.. }}}
::
$ python cgitb_local_vars.py
<type 'exceptions.ZeroDivisionError'>
Python 2.7: /Users/dhellmann/.virtualenvs/pymotw/bin/python
Sun Oct 24 08:53:18 2010
A problem occurred in a Python script. Here is the sequence of
function calls leading up to the error, in the order they occurred.
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_local_vars.py in <module>()
16 def func1(a, b):
17 c = b - 5
18 return func2(a, c)
19
20 func1(1, 5)
func1 = <function func1>
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_local_vars.py in func1(a=1, b=5)
16 def func1(a, b):
17 c = b - 5
18 return func2(a, c)
19
20 func1(1, 5)
global func2 = <function func2>
a = 1
c = 0
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_local_vars.py in func2(a=1, divisor=0)
12
13 def func2(a, divisor):
14 return a / divisor
15
16 def func1(a, b):
a = 1
divisor = 0
<type 'exceptions.ZeroDivisionError'>: integer division or modulo by zero
__class__ = <type 'exceptions.ZeroDivisionError'>
__delattr__ = <method-wrapper '__delattr__' of exceptions.ZeroDivisionError object>
__dict__ = {}
__doc__ = 'Second argument to a division or modulo operation was zero.'
__format__ = <built-in method __format__ of exceptions.ZeroDivisionError object>
__getattribute__ = <method-wrapper '__getattribute__' of exceptions.ZeroDivisionError object>
__getitem__ = <method-wrapper '__getitem__' of exceptions.ZeroDivisionError object>
__getslice__ = <method-wrapper '__getslice__' of exceptions.ZeroDivisionError object>
__hash__ = <method-wrapper '__hash__' of exceptions.ZeroDivisionError object>
__init__ = <method-wrapper '__init__' of exceptions.ZeroDivisionError object>
__new__ = <built-in method __new__ of type object>
__reduce__ = <built-in method __reduce__ of exceptions.ZeroDivisionError object>
__reduce_ex__ = <built-in method __reduce_ex__ of exceptions.ZeroDivisionError object>
__repr__ = <method-wrapper '__repr__' of exceptions.ZeroDivisionError object>
__setattr__ = <method-wrapper '__setattr__' of exceptions.ZeroDivisionError object>
__setstate__ = <built-in method __setstate__ of exceptions.ZeroDivisionError object>
__sizeof__ = <built-in method __sizeof__ of exceptions.ZeroDivisionError object>
__str__ = <method-wrapper '__str__' of exceptions.ZeroDivisionError object>
__subclasshook__ = <built-in method __subclasshook__ of type object>
__unicode__ = <built-in method __unicode__ of exceptions.ZeroDivisionError object>
args = ('integer division or modulo by zero',)
message = 'integer division or modulo by zero'
The above is a description of an error in a Python program. Here is
the original traceback:
Traceback (most recent call last):
File "cgitb_local_vars.py", line 20, in <module>
func1(1, 5)
File "cgitb_local_vars.py", line 18, in func1
return func2(a, c)
File "cgitb_local_vars.py", line 14, in func2
return a / divisor
ZeroDivisionError: integer division or modulo by zero
.. {{{end}}}
The code in :mod:`cgitb` that examines the variables used in the stack
frame leading to the error is smart enough to evaluate object
attributes to display them, too.
.. include:: cgitb_with_classes.py
:literal:
:start-after: #end_pymotw_header
Here we see that ``self.a`` and ``self.b`` are involved in the
error-prone code.
.. {{{cog
.. cog.out(run_script(cog.inFile, 'cgitb_with_classes.py', ignore_error=True))
.. }}}
::
$ python cgitb_with_classes.py
<type 'exceptions.ZeroDivisionError'>
Python 2.7: /Users/dhellmann/.virtualenvs/pymotw/bin/python
Sun Oct 24 08:53:18 2010
A problem occurred in a Python script. Here is the sequence of
function calls leading up to the error, in the order they occurred.
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_with_classes.py in <module>()
24 return
25
26 o = BrokenClass(1, 0)
27
28
o undefined
BrokenClass = <class '__main__.BrokenClass'>
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_with_classes.py in __init__(self=<__main__.BrokenClass object>, a=1, b=0)
21 self.b = b
22 self.c = self.a * self.b
23 self.d = self.a / self.b
24 return
25
self = <__main__.BrokenClass object>
self.d undefined
self.a = 1
self.b = 0
<type 'exceptions.ZeroDivisionError'>: integer division or modulo by zero
__class__ = <type 'exceptions.ZeroDivisionError'>
__delattr__ = <method-wrapper '__delattr__' of exceptions.ZeroDivisionError object>
__dict__ = {}
__doc__ = 'Second argument to a division or modulo operation was zero.'
__format__ = <built-in method __format__ of exceptions.ZeroDivisionError object>
__getattribute__ = <method-wrapper '__getattribute__' of exceptions.ZeroDivisionError object>
__getitem__ = <method-wrapper '__getitem__' of exceptions.ZeroDivisionError object>
__getslice__ = <method-wrapper '__getslice__' of exceptions.ZeroDivisionError object>
__hash__ = <method-wrapper '__hash__' of exceptions.ZeroDivisionError object>
__init__ = <method-wrapper '__init__' of exceptions.ZeroDivisionError object>
__new__ = <built-in method __new__ of type object>
__reduce__ = <built-in method __reduce__ of exceptions.ZeroDivisionError object>
__reduce_ex__ = <built-in method __reduce_ex__ of exceptions.ZeroDivisionError object>
__repr__ = <method-wrapper '__repr__' of exceptions.ZeroDivisionError object>
__setattr__ = <method-wrapper '__setattr__' of exceptions.ZeroDivisionError object>
__setstate__ = <built-in method __setstate__ of exceptions.ZeroDivisionError object>
__sizeof__ = <built-in method __sizeof__ of exceptions.ZeroDivisionError object>
__str__ = <method-wrapper '__str__' of exceptions.ZeroDivisionError object>
__subclasshook__ = <built-in method __subclasshook__ of type object>
__unicode__ = <built-in method __unicode__ of exceptions.ZeroDivisionError object>
args = ('integer division or modulo by zero',)
message = 'integer division or modulo by zero'
The above is a description of an error in a Python program. Here is
the original traceback:
Traceback (most recent call last):
File "cgitb_with_classes.py", line 26, in <module>
o = BrokenClass(1, 0)
File "cgitb_with_classes.py", line 23, in __init__
self.d = self.a / self.b
ZeroDivisionError: integer division or modulo by zero
.. {{{end}}}
Adding More Context
===================
Suppose your function includes a lot of inline comments, whitespace,
or other code that makes it very long. Having the default of 5 lines
of context may not be enough help in that case, if the body of the
function is pushed out of the code window displayed. Using a larger
context value when enabling cgitb gets around this.
.. include:: cgitb_more_context.py
:literal:
:start-after: #end_pymotw_header
You can pass *context* to :func:`enable()` to control the amount of
code displayed for each line of the traceback.
.. {{{cog
.. cog.out(run_script(cog.inFile, 'cgitb_more_context.py 5', ignore_error=True))
.. }}}
::
$ python cgitb_more_context.py 5
<type 'exceptions.ZeroDivisionError'>
Python 2.7: /Users/dhellmann/.virtualenvs/pymotw/bin/python
Sun Oct 24 08:53:19 2010
A problem occurred in a Python script. Here is the sequence of
function calls leading up to the error, in the order they occurred.
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_more_context.py in <module>()
24 # goes
25 # here.
26 return func2(a, c)
27
28 func1(1, 5)
func1 = <function func1>
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_more_context.py in func1(a=1, b=5)
24 # goes
25 # here.
26 return func2(a, c)
27
28 func1(1, 5)
global func2 = <function func2>
a = 1
c = 0
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_more_context.py in func2(a=1, divisor=0)
15
16 def func2(a, divisor):
17 return a / divisor
18
19 def func1(a, b):
a = 1
divisor = 0
<type 'exceptions.ZeroDivisionError'>: integer division or modulo by zero
__class__ = <type 'exceptions.ZeroDivisionError'>
__delattr__ = <method-wrapper '__delattr__' of exceptions.ZeroDivisionError object>
__dict__ = {}
__doc__ = 'Second argument to a division or modulo operation was zero.'
__format__ = <built-in method __format__ of exceptions.ZeroDivisionError object>
__getattribute__ = <method-wrapper '__getattribute__' of exceptions.ZeroDivisionError object>
__getitem__ = <method-wrapper '__getitem__' of exceptions.ZeroDivisionError object>
__getslice__ = <method-wrapper '__getslice__' of exceptions.ZeroDivisionError object>
__hash__ = <method-wrapper '__hash__' of exceptions.ZeroDivisionError object>
__init__ = <method-wrapper '__init__' of exceptions.ZeroDivisionError object>
__new__ = <built-in method __new__ of type object>
__reduce__ = <built-in method __reduce__ of exceptions.ZeroDivisionError object>
__reduce_ex__ = <built-in method __reduce_ex__ of exceptions.ZeroDivisionError object>
__repr__ = <method-wrapper '__repr__' of exceptions.ZeroDivisionError object>
__setattr__ = <method-wrapper '__setattr__' of exceptions.ZeroDivisionError object>
__setstate__ = <built-in method __setstate__ of exceptions.ZeroDivisionError object>
__sizeof__ = <built-in method __sizeof__ of exceptions.ZeroDivisionError object>
__str__ = <method-wrapper '__str__' of exceptions.ZeroDivisionError object>
__subclasshook__ = <built-in method __subclasshook__ of type object>
__unicode__ = <built-in method __unicode__ of exceptions.ZeroDivisionError object>
args = ('integer division or modulo by zero',)
message = 'integer division or modulo by zero'
The above is a description of an error in a Python program. Here is
the original traceback:
Traceback (most recent call last):
File "cgitb_more_context.py", line 28, in <module>
func1(1, 5)
File "cgitb_more_context.py", line 26, in func1
return func2(a, c)
File "cgitb_more_context.py", line 17, in func2
return a / divisor
ZeroDivisionError: integer division or modulo by zero
.. {{{end}}}
Increasing the value gets us enough of the function that we can spot
the problem in the code, again.
.. {{{cog
.. cog.out(run_script(cog.inFile, 'cgitb_more_context.py 10', ignore_error=True))
.. }}}
::
$ python cgitb_more_context.py 10
<type 'exceptions.ZeroDivisionError'>
Python 2.7: /Users/dhellmann/.virtualenvs/pymotw/bin/python
Sun Oct 24 08:53:19 2010
A problem occurred in a Python script. Here is the sequence of
function calls leading up to the error, in the order they occurred.
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_more_context.py in <module>()
19 def func1(a, b):
20 c = b - 5
21 # Really
22 # long
23 # comment
24 # goes
25 # here.
26 return func2(a, c)
27
28 func1(1, 5)
func1 = <function func1>
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_more_context.py in func1(a=1, b=5)
19 def func1(a, b):
20 c = b - 5
21 # Really
22 # long
23 # comment
24 # goes
25 # here.
26 return func2(a, c)
27
28 func1(1, 5)
global func2 = <function func2>
a = 1
c = 0
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_more_context.py in func2(a=1, divisor=0)
12
13 context_length = int(sys.argv[1])
14 cgitb.enable(format='text', context=context_length)
15
16 def func2(a, divisor):
17 return a / divisor
18
19 def func1(a, b):
20 c = b - 5
21 # Really
a = 1
divisor = 0
<type 'exceptions.ZeroDivisionError'>: integer division or modulo by zero
__class__ = <type 'exceptions.ZeroDivisionError'>
__delattr__ = <method-wrapper '__delattr__' of exceptions.ZeroDivisionError object>
__dict__ = {}
__doc__ = 'Second argument to a division or modulo operation was zero.'
__format__ = <built-in method __format__ of exceptions.ZeroDivisionError object>
__getattribute__ = <method-wrapper '__getattribute__' of exceptions.ZeroDivisionError object>
__getitem__ = <method-wrapper '__getitem__' of exceptions.ZeroDivisionError object>
__getslice__ = <method-wrapper '__getslice__' of exceptions.ZeroDivisionError object>
__hash__ = <method-wrapper '__hash__' of exceptions.ZeroDivisionError object>
__init__ = <method-wrapper '__init__' of exceptions.ZeroDivisionError object>
__new__ = <built-in method __new__ of type object>
__reduce__ = <built-in method __reduce__ of exceptions.ZeroDivisionError object>
__reduce_ex__ = <built-in method __reduce_ex__ of exceptions.ZeroDivisionError object>
__repr__ = <method-wrapper '__repr__' of exceptions.ZeroDivisionError object>
__setattr__ = <method-wrapper '__setattr__' of exceptions.ZeroDivisionError object>
__setstate__ = <built-in method __setstate__ of exceptions.ZeroDivisionError object>
__sizeof__ = <built-in method __sizeof__ of exceptions.ZeroDivisionError object>
__str__ = <method-wrapper '__str__' of exceptions.ZeroDivisionError object>
__subclasshook__ = <built-in method __subclasshook__ of type object>
__unicode__ = <built-in method __unicode__ of exceptions.ZeroDivisionError object>
args = ('integer division or modulo by zero',)
message = 'integer division or modulo by zero'
The above is a description of an error in a Python program. Here is
the original traceback:
Traceback (most recent call last):
File "cgitb_more_context.py", line 28, in <module>
func1(1, 5)
File "cgitb_more_context.py", line 26, in func1
return func2(a, c)
File "cgitb_more_context.py", line 17, in func2
return a / divisor
ZeroDivisionError: integer division or modulo by zero
.. {{{end}}}
Exception Properties
====================
In addition to the local variables from each stack frame, :mod:`cgitb`
shows all properties of the exception object. If you have a custom
exception type with extra properties, they are printed as part of the
error report.
.. include:: cgitb_exception_properties.py
:literal:
:start-after: #end_pymotw_header
In this example, the *bad_value* property is included along with the
standard *message* and *args* values.
.. {{{cog
.. cog.out(run_script(cog.inFile, 'cgitb_exception_properties.py', ignore_error=True))
.. }}}
::
$ python cgitb_exception_properties.py
<class '__main__.MyException'>
Python 2.7: /Users/dhellmann/.virtualenvs/pymotw/bin/python
Sun Oct 24 08:53:19 2010
A problem occurred in a Python script. Here is the sequence of
function calls leading up to the error, in the order they occurred.
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_exception_properties.py in <module>()
18 self.bad_value = bad_value
19 Exception.__init__(self, message)
20 return
21
22 raise MyException('Normal message', bad_value=99)
MyException = <class '__main__.MyException'>
bad_value undefined
<class '__main__.MyException'>: Normal message
__class__ = <class '__main__.MyException'>
__delattr__ = <method-wrapper '__delattr__' of MyException object>
__dict__ = {'bad_value': 99}
__doc__ = 'Add extra properties to a special exception\n '
__format__ = <built-in method __format__ of MyException object>
__getattribute__ = <method-wrapper '__getattribute__' of MyException object>
__getitem__ = <method-wrapper '__getitem__' of MyException object>
__getslice__ = <method-wrapper '__getslice__' of MyException object>
__hash__ = <method-wrapper '__hash__' of MyException object>
__init__ = <bound method MyException.__init__ of MyException('Normal message',)>
__module__ = '__main__'
__new__ = <built-in method __new__ of type object>
__reduce__ = <built-in method __reduce__ of MyException object>
__reduce_ex__ = <built-in method __reduce_ex__ of MyException object>
__repr__ = <method-wrapper '__repr__' of MyException object>
__setattr__ = <method-wrapper '__setattr__' of MyException object>
__setstate__ = <built-in method __setstate__ of MyException object>
__sizeof__ = <built-in method __sizeof__ of MyException object>
__str__ = <method-wrapper '__str__' of MyException object>
__subclasshook__ = <built-in method __subclasshook__ of type object>
__unicode__ = <built-in method __unicode__ of MyException object>
__weakref__ = None
args = ('Normal message',)
bad_value = 99
message = 'Normal message'
The above is a description of an error in a Python program. Here is
the original traceback:
Traceback (most recent call last):
File "cgitb_exception_properties.py", line 22, in <module>
raise MyException('Normal message', bad_value=99)
MyException: Normal message
.. {{{end}}}
Logging Tracebacks
==================
For many situations, printing the traceback details to standard error
is the best resolution. In a production system, however, logging the
errors is even better. :func:`enable()` includes an optional
argument, *logdir*, to enable error logging. When a directory name is
provided, each exception is logged to its own file in the given
directory.
.. include:: cgitb_log_exception.py
:literal:
:start-after: #end_pymotw_header
Even though the error display is suppressed, a message is printed
describing where to go to find the error log.
.. {{{cog
.. path('PyMOTW/cgitb/LOGS').rmtree()
.. sh('mkdir -p PyMOTW/cgitb/LOGS')
.. cog.out(run_script(cog.inFile, 'cgitb_log_exception.py', ignore_error=True))
.. cog.out(run_script(cog.inFile, 'ls LOGS', interpreter=None, include_prefix=False))
.. cog.out(run_script(cog.inFile, 'cat LOGS/*.txt', interpreter=None, include_prefix=False))
.. }}}
::
$ python cgitb_log_exception.py
<p>A problem occurred in a Python script.
<p> /Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/LOGS/tmpLjKFFz.txt contains the description of this error.
$ ls LOGS
tmpLjKFFz.txt
$ cat LOGS/*.txt
<type 'exceptions.ZeroDivisionError'>
Python 2.7: /Users/dhellmann/.virtualenvs/pymotw/bin/python
Sun Oct 24 08:53:19 2010
A problem occurred in a Python script. Here is the sequence of
function calls leading up to the error, in the order they occurred.
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_log_exception.py in <module>()
21 def func1(a, b):
22 c = b - 5
23 return func2(a, c)
24
25 func1(1, 5)
func1 = <function func1>
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_log_exception.py in func1(a=1, b=5)
21 def func1(a, b):
22 c = b - 5
23 return func2(a, c)
24
25 func1(1, 5)
global func2 = <function func2>
a = 1
c = 0
/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/cgitb/cgitb_log_exception.py in func2(a=1, divisor=0)
17
18 def func2(a, divisor):
19 return a / divisor
20
21 def func1(a, b):
a = 1
divisor = 0
<type 'exceptions.ZeroDivisionError'>: integer division or modulo by zero
__class__ = <type 'exceptions.ZeroDivisionError'>
__delattr__ = <method-wrapper '__delattr__' of exceptions.ZeroDivisionError object>
__dict__ = {}
__doc__ = 'Second argument to a division or modulo operation was zero.'
__format__ = <built-in method __format__ of exceptions.ZeroDivisionError object>
__getattribute__ = <method-wrapper '__getattribute__' of exceptions.ZeroDivisionError object>
__getitem__ = <method-wrapper '__getitem__' of exceptions.ZeroDivisionError object>
__getslice__ = <method-wrapper '__getslice__' of exceptions.ZeroDivisionError object>
__hash__ = <method-wrapper '__hash__' of exceptions.ZeroDivisionError object>
__init__ = <method-wrapper '__init__' of exceptions.ZeroDivisionError object>
__new__ = <built-in method __new__ of type object>
__reduce__ = <built-in method __reduce__ of exceptions.ZeroDivisionError object>
__reduce_ex__ = <built-in method __reduce_ex__ of exceptions.ZeroDivisionError object>
__repr__ = <method-wrapper '__repr__' of exceptions.ZeroDivisionError object>
__setattr__ = <method-wrapper '__setattr__' of exceptions.ZeroDivisionError object>
__setstate__ = <built-in method __setstate__ of exceptions.ZeroDivisionError object>
__sizeof__ = <built-in method __sizeof__ of exceptions.ZeroDivisionError object>
__str__ = <method-wrapper '__str__' of exceptions.ZeroDivisionError object>
__subclasshook__ = <built-in method __subclasshook__ of type object>
__unicode__ = <built-in method __unicode__ of exceptions.ZeroDivisionError object>
args = ('integer division or modulo by zero',)
message = 'integer division or modulo by zero'
The above is a description of an error in a Python program. Here is
the original traceback:
Traceback (most recent call last):
File "cgitb_log_exception.py", line 25, in <module>
func1(1, 5)
File "cgitb_log_exception.py", line 23, in func1
return func2(a, c)
File "cgitb_log_exception.py", line 19, in func2
return a / divisor
ZeroDivisionError: integer division or modulo by zero
.. {{{end}}}
HTML Output
===========
Because :mod:`cgitb` was originally developed for handling exceptions
in web apps, no discussion would be complete without an example of the
HTML output it produces.
.. include:: cgitb_html_output.py
:literal:
:start-after: #end_pymotw_header
By leaving out the *format* argument (or specifying ``html``), the
traceback format changes to HTML output.
.. image:: html_error.png
.. seealso::
`cgitb <http://docs.python.org/library/cgitb.html>`_
The standard library documentation for this module.
:mod:`traceback`
Standard library module for working with tracebacks.
:mod:`inspect`
The inspect module includes more functions for examining the
stack.
:mod:`sys`
The sys module provides access to the current exception value
and the ``excepthook`` handler invoked when an exception
occurs.
`Improved traceback module <http://thread.gmane.org/gmane.comp.python.devel/110326>`_
Python-dev discussion of improvements to the traceback module
and related enhancements other developers use locally.