[Python-Dev] why string exceptions are bad

[Jewett, Jim J]

>> Out of curiosity, why are string exceptions going away?  

> Probably, originally, for many of the reasons stated here.  
> That people expected equality tests in the except clause
> and were tripped up by the identity test performed. 

Trying to catch (some, but not all) exceptions from another 
module can be difficult if the module raises strings.  At
best, you catch everything, test with == (even though "is" 
seemed to work in your tests), and maybe reraise.

If they start raising

	"Error:  You requested 7 but the quota is 6"

you have to regex match.

If the "same" error is raised several places (or by several
different modules), there will eventually be a typo.

	"Error: That was not a string"
	"Error: That was not a string."
	"Error: That was mot a string."
	"Error  That was not a string."
	"Error: That wasn't a string"
	"ERROR: That was not a string"

A class can be defined in a single place (and imported); 
a typo in the 47th raise statement will show up as a syntax
error instead of a runtime bug.

-jJ