[Python-Dev] context manager - generator interaction? (original) (raw)

Steve Holden steve at holdenweb.com
Fri Apr 6 13🔞26 CEST 2007

Guido van Rossum wrote:

On 4/5/07, Raymond Hettinger <python at rcn.com> wrote:

Guido van Rossum wrote:

Isn't this violating the rule that a try/except should only enclose the smallest expression where the exception is expected? Yeah, and I keep finding myself wanting to hyperlink to that "rule" in the official docs, but it only seems to be written down in developer's heads. Can we get that into the Language Ref somewhere? Maybe on the http://docs.python.org/ref/try.html page? I'll add a snippet to the tutorial with advice on try/except. I don't think it should go in the main documentation because it is really more of a suggestion or technique than an actual rule. Also, there are plenty of other situations where the "rule" doesn't apply. I see a lot of code written by Googlers who are not (yet) experienced Python users. Overly wide try/except clauses are a common mistake, and it is nearly always easy to apply this rule. I would argue, as a style issue, for making this rule the norm, and require deviations to be thought through very carefully. This rule has no place in a pure language reference manual. But it certainly deserves mention in any form of more practical documentation, be it a tutorial or a more advanced programming manual. PEP 8 would (also? I don't see this being relevant to the reference manual, but that's not a biggie) seem a logical place for this information to go, since it deals with try-except. I'd suggest something along the lines of:

A frequent beginner's error is to make the scope of a try clause too broad, covering a larger span of code that necessary so that the except clause is triggered by unanticipated exceptions. Try to ensure that a try clause applies to the fewest possible statements to avoid these issues.

regards Steve

Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC/Ltd http://www.holdenweb.com Skype: holdenweb http://del.icio.us/steve.holden Recent Ramblings http://holdenweb.blogspot.com

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