using the python traceback type

Question

By calling sys.exc_info() when an exception is handled a 3-tuple is returned containing the exception class, the exception object and the traceback.

This is also evident by the documentation of sys.exc_info:

This function returns a tuple of three values that give information about the exception that is currently being handled. ... the values returned are (type, value, traceback). ... traceback gets a traceback object (see the Reference Manual) which encapsulates the call stack at the point where the exception originally occurred.

I want to use the type traceback which is used to create the third variable in the aforementioned exc_info return value but can't find where it's defined.

My question is, therefore, where is the traceback type available for python scripts?

EDIT:

I would like to use the traceback type to define a PyQt signal. PyQt Signals are defined by specifying the signal name together with the types of parameters passed. I do not need to create an object of that type, only use it in a manner similar to an isinstance call.

Answer 1

bad news, even if you can get the class of the traceback object like this:

import sys

try:
    raise Exception
except:
    tb = sys.exc_info()[2]

print(tb.__class__)

result:

<class 'traceback'>

when you try:

tb.__class__()

you get:

TypeError: cannot create 'traceback' instances

so the traceback type cannot be instanciated externally, probably because you'd need to access python internals to do so (and attributes are read-only even tb_lineno so not possible to "reuse" an instance either)

Answer 2

You can use traceback.format_exc() or sys.exc_info() like :

try:
    raise TypeError("Error !?!")
except Exception:
    print(traceback.format_exc())
    # or
    print(sys.exc_info()[2])