[EMAIL PROTECTED] a écrit :
(snip)
Here is an example: a simple query tool for a tiny "mock SQL"
relational database. With a method (called "select_all") you can
perform the equivalent of a select query on the database. The contents
of the query are specified with triples of the form
[field, comparison_operator, value]
for instance ['name', operator.equals, cmd_name]. You can also specify
an "order by" field which is None by default. In the code written,
there is an assertion that the order-by field is either None or a
valid field name (we can't order by a nonexistent field!). If the
assertion isn't there, then I will get an error on this line:
key_extractor = KeyExtractor(q_column_names.index(order_by_column))
In this particular case, I will get a ValueError (what does ValueError
mean again? And what is this KeyExtractor?) since the index method
will fail. I wrote the tiny relational database a long time ago, and I
really don't want to put pressure on my mental cache by thinking about
the internal logic of this chunk of code. After scratching my head for
a while, I'll probably figure it out. Now imagine that you instead get
an error on this line:
assert order_by_column in q_column_names
>
Now the programming error slaps me with a fish and yells "STOP! YOU
CAN'T ORDER BY A FIELD THAT DOESN'T EXIST!!!".
As far as I'm concerned, this is a case where I would explicitely raise
an exception (either a ValueError with an explicit message or a
library-defined exception type).
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