How to save traceback / sys.exc_info() values in a variable?

This is how I do it:

>>> import traceback
>>> try:
...   int('k')
... except:
...   var = traceback.format_exc()
... 
>>> print(var)
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
ValueError: invalid literal for int() with base 10: 'k'

You should however take a look at the traceback documentation, as you might find there more suitable methods, depending to how you want to process your variable afterwards...

sys.exc_info() returns a tuple with three values (type, value, traceback).

1. Here type gets the exception type of the Exception being handled
2. value is the arguments that are being passed to constructor of exception class
3. traceback contains the stack information like where the exception occurred etc.

For Example, In the following program

try:

    a = 1/0

except Exception,e:

    exc_tuple = sys.exc_info()

Now If we print the tuple the values will be this.

1. exc_tuple[0] value will be "ZeroDivisionError"
2. exc_tuple[1] value will be "integer division or modulo by zero" (String passed as parameter to the exception class)
3. exc_tuple[2] value will be "trackback object at (some memory address)"

The above details can also be fetched by simply printing the exception in string format.

print str(e)

Use traceback.extract_stack() if you want convenient access to module and function names and line numbers.

Use ''.join(traceback.format_stack()) if you just want a string that looks like the traceback.print_stack() output.

Notice that even with ''.join() you will get a multi-line string, since the elements of format_stack() contain \n. See output below.

Remember to import traceback.

Here's the output from traceback.extract_stack(). Formatting added for readability.

>>> traceback.extract_stack()
[
   ('<string>', 1, '<module>', None),
   ('C:\\Python\\lib\\idlelib\\run.py', 126, 'main', 'ret = method(*args, **kwargs)'),
   ('C:\\Python\\lib\\idlelib\\run.py', 353, 'runcode', 'exec(code, self.locals)'),
   ('<pyshell#1>', 1, '<module>', None)
]

Here's the output from ''.join(traceback.format_stack()). Formatting added for readability.

>>> ''.join(traceback.format_stack())
'  File "<string>", line 1, in <module>\n
   File "C:\\Python\\lib\\idlelib\\run.py", line 126, in main\n
       ret = method(*args, **kwargs)\n
   File "C:\\Python\\lib\\idlelib\\run.py", line 353, in runcode\n
       exec(code, self.locals)\n  File "<pyshell#2>", line 1, in <module>\n'

The object can be used as a parameter in Exception.with_traceback() function:

except Exception as e:
    tb = sys.exc_info()
    print(e.with_traceback(tb[2]))