Typing arguments in python

[Erik Max Francis]

"A. Lloyd Flanagan" wrote:

> An assert is technically a
> statement that a certain condition can't happen under any
> circumstances.  It's used to verify that the code in the function has
> the expected effect on the state of the program.  But being called
> with an incorrect parameter is NOT a flaw in the code that contains
> the assert -- it's a problem with the caller.  Basically, instead of
> saying, "hey, buddy, that parameter is wrong" you're now saying
> "whoops, there's a bug in my code somewhere".  For a bad parameter you
> should raise ValueError or something similar, not AssertionError.

Some programming houses break asserts into two types:  logic asserts and
data asserts.  Logic asserts are the traditional "can't happen; if it
did something is disastrously wrong" variety, but data asserts are the
"you sent me bad data, dummy" form.  This way you select differing
behavior (ignore them completely, print a warning message in a log file,
or abort immediately) on each of them separately.

-- 
 Erik Max Francis / max at alcyone.com / http://www.alcyone.com/max/
 __ San Jose, CA, USA / 37 20 N 121 53 W / &tSftDotIotE
/  \ Would a harvest from my heart / Find its season
\__/ Sandra St. Victor
    Python chess module / http://www.alcyone.com/pyos/chess/
 A chess game adjudicator in Python.