Professional IronPython

sys.exc_info()
: Returns a 
tuple
containing three items:
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➤
type
: The type of the error, such as 
ZeroDivisionError
. You can find a list of all 
standard exception types in the 
exceptions
module.
➤
➤
value
: The human readable string that defines the error. For example,
a 
ZeroDivisionError
might provide
ZeroDivisionError(‘Attempted to divide by zero.‘,)
as a value.
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Obtaining Error Information
 
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253
➤
➤
traceback
: An object that describes the stack trace for an exception. Normally, you 
won’t use this information directly unless you truly need to obtain the stack trace 
information, which can prove difficult. If you need stack trace information, consider 
using the 
traceback
module features instead (see the “Using the traceback Module” 
section of this chapter for details).
➤
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sys.exc_clear()
: Clears the existing exceptions from the current thread. After you call this 
function, 
sys.exc_info()
returns 
None
for all three elements in the 
tuple
.
The 
sys.exc_info()
function isn’t very hard to use, but you can’t really try it out by executing it 
directly in the IronPython console. You need to place it within a 
try...except
structure instead. 
The following code shows a quick demonstration you can type directly into the console window.
try:
5/0
except:
type, value = sys.exc_info()[:2]
print type
print value
The example uses a simple division by zero to create an exception. As previously noted, you normally 
need just the first two elements of the 
tuple
, which you can obtain using 
sys.exc_info()[:2]
. When 
you execute this code, you see the following output.

Attempted to divide by zero.
Some IronPython 
sys
module functions affect only the interactive thread (which means they’re 
safe to use in multithreaded applications because there is only one interactive thread in any given 
session). You could use these functions to determine the current type, value, and 
traceback
for an 
exception, but only for the interactive session, which means these functions are completely useless 
for your application. In most cases, you avoid using these three functions.
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sys.last_traceback()
➤
sys.last_type()
➤
➤
sys.last_value()
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You could run into problems when working with some functions in the 
sys
module. For example, 
these three functions are global, which means they aren’t specific to the current thread and are 
therefore, unsafe to use in a multithreaded application.
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sys.exc_type()
➤
sys.exc_value()
➤
➤
sys.exc_traceback()
➤
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Interestingly enough, these three functions are also listed as deprecated (outdated) in most Python 
implementations (including IronPython). As with all IronPython modules, you also have access to 
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