[Tutor] Key Error
alan.gauld at btinternet.com
Mon Jul 9 09:22:05 CEST 2007
"jim stockford" <jim at well.com> wrote
>> (The tests at the end are poorly written too.
> If you'd be willing to share your strong words, I'd
> be grateful to learn better alternatives.
OK, The strong words referred to the entire piece and
the biggest error was the lack of try/except or get().
However the tests are badly done IMHO for several
if wssd<-989. or wspd<-989. or wmax<-989.: break
if wspd==0.: break
1) Both sets of tests result in a break so the last test
should be combined with the others in a single line.
(as a sub point I'd also prefer to see both tests on
wspd placed together for ease of maintenance)
2) The values are floating point but the programmer has
lazily omited the end zero which makes it very hard to
spot the trailing decimal point.
3) The last equality test is inherently unreliable when
using floating point values since if the value were derived
by calciulation it might be 'nearly zero', the best way to
check equality for floats is to test within a range. (If this
case is guaranteed safe I would expect a comment to
explain why, because it's such an unusual situation...)
4) The spacing between the < and minus sign is non
existent which could lead to the combination being read
as a <- arrow sign. Now inPyton that doesn't mean
anything but in other languages does, so a reader
not familiar with Python (like our OP) might be
misdirected, whereas a simple space would remove
Some might also object to the break being on the
same line as the test but personally I don't object to
that. But the points above all have real impact on legibility,
maintainability and, potentially, reliability.
We wouldn't normally expect to see such pickiness
in this list because its aimed at beginners, but if this
is production code, and from the look of it, in the
telecomms market - which usually demands very high
standards, then the quality should be much higher.
I'd prefer the tests to be written like this:
e = 0.0000000000001
if -e <= wspd <= e or
wspd < -989.0 or
wssd < -989.0 or
wmax < -989.0:
Its more typing and more room but less ambiguous
and easier to read IMHO.
More information about the Tutor