On Mon, Aug 27, 2012 at 6:33 PM, Japhy Bartlett<[email protected]> wrote:
something like:
def _validate_int(obj):
"""Raise an exception if obj is not an integer."""
m = int(obj + 0) # May raise TypeError.
if obj != m:
raise ValueError('expected an integer but got %r' % obj)
is a really awkward way to test if something's an integer,
Not really. It's trivially easy: just call
_validate_int(x)
You don't have to inspect a return result and decide what to do. If it
returns, x is an integer. If it doesn't, you get a nice exception:
TypeError for non-numeric objects
ValueError for non-integer numbers, or float/Decimal NANs and infinities
and checking
types in general is usually a sign of larger flaws in laying out useful
code.
That's probably true, but especially for library code, that's not always
the case. I'm merely following the usual best-practice of Python code (to
the best of my ability), as seen in the standard library:
py> import math
py> math.factorial(2.5)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: factorial() only accepts integral values
py> math.factorial("2")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: an integer is required
What would you expect factorial to do in these cases, if not raise an
exception?
Speaking of argument validation, this amuses me:
http://thedailywtf.com/Articles/Argument_About_Argument_Validation.aspx
--
Steven
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