On Jan 7, 2009, at 12:24 PM, Adal Chiriliuc wrote:
Hello,
Me and my colleagues are having an discussion about the best way to
code a function (more Pythonic).
Here is the offending function:
def find(field, order):
....if not isinstance(order, bool):
........raise ValueError("order must be a bool")
....order_by = "asc" if order else "desc"
....return _find(field + "+" + order_by)
We are not sure what's the best practice here. Should we or should we
not check the type of the "order" variable, which should be a bool?
IMHO you should not.
The pro argument was that if a new programmer comes and passes a
wrongly typed argument, he will get a silent failure.
"Wrongly typed" is a matter of opinion. The following values also
evaluate to False when converted to bool:
None
[]
()
""
{}
To me, they're just as false as False is, if you catch my meaning. I
would not like to have to convert them to bool to be able to use them
when calling your function.
Imagine this scenario --
order = read_order_from_preferences_xml_file(default_value = None)
# order is now "ascending" or None
find(the_field_name, order)
It seems logical to pass a string or None in this case without
converting them to bool.
You might feel more comfortable if the parameter was called
"is_ordered", which would at least imply that it is a boolean so that
someone unfamiliar with the interface would be less tempted to pass
something like the last part of an ORDER BY statement, like
"last_name, first_name, age DESC".
I can understand your temptation to enforce bool-ness, but you have a
very good point about this one function then being different from all
of the others that aren't as picky.
HTH
Philip
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