The sys module provides one function that
provides the details of the exception that was raised. Programs with
exception handling will occasionally use this function.
The sys.exc_info function returns a
3-tuple with the exception, the exception's
parameter, and a traceback object that pinpoints the line of Python that
raised the exception. This can be used something like the following
not-very-good example.
Example 17.5. exception2.py
import sys
import math
a= 2
b= 2
c= 1
try:
x1= (-b+math.sqrt(b*b-4*a*c))/(2*a)
x2= (-b-math.sqrt(b*b-4*a*c))/(2*a)
print x1, x2
except:
e,p,t= sys.exc_info()
print e,p
This uses
multiple assignment
to capture the
three elements of the sys.exc_info
tuple, the exception itself in
e, the parameter in p and a Python
traceback object in t.
This "catch-all" exception handler in this example is a bad
policy. It may catch exceptions which are better left uncaught. We'll
look at these kinds of exceptions in the section called “Built-in Exceptions”. For example, a
RuntimeError is something you should not
bother catching.
