Question on try/except

[Dan]

While perusing sre.py in the standard library, I came upon this snippet
of code in the _compile() function definition:

try:
p = sre_compile.compile(pattern, flags)
except error, v:
raise error, v # invalid expression

Is there some particular use in catching an exception and immediately
re-raising it? Why catch it at all?

/Dan

 

[Kirk McDonald]

While perusing sre.py in the standard library, I came upon this snippet
of code in the _compile() function definition:

try:
p = sre_compile.compile(pattern, flags)
except error, v:
raise error, v # invalid expression

Is there some particular use in catching an exception and immediately
re-raising it? Why catch it at all?

/Dan

All I can think of is that it changes the traceback to point to the
re-raise and not the original raise.

-Kirk McDonald

 

[Patrick Maupin]

All I can think of is that it changes the traceback to point to the
re-raise and not the original raise.

I've used this technique before. It is very useful where (as in the
original re example) recursion might cause a large traceback, and the
error is probably caused by the caller's code. Using this technique
can keep the visible portion of the traceback relevant to the problem
at hand.

Regards,
Pat