Alex Hall writes:
> Do you not usually refactor duplicated code?
Taking "you" as generic: it depends.
> What *do* you refactor?
Code is expressive. In cases where the duplication results in
equivalent objects, I habitually refactor. When the process is
important to express and the duplication is syntactic, I will prefer
an explicit but idiomatic syntax repeated in unrelated contexts. Thus
I generally wouldn't consider your list to be "duplicated code that
cries out for refactoring."
When the process is complex then I'd refactor. Detecting an out of
bounds index is complex enough because of fenceposts and negative
indicies, although I probably wouldn't notice the negative indicies
until they bit me (and in that case wouldn't refactor until bitten).
> > I'd find it more interesting if there were a larger variety of
> > cases
>
> This sort of sounds like the problem. The examples aren't meant to be
> interesting.
"You [both] keep using that word but I do not think [Steven] means
what you think it means." (pace, Inigo)
I find the long list of examples with mostly identical syntax
*unpersuasive* for two reasons. First, if you're going to bounds
check array indicies explicitly (rather than allow IndexError to
"bubble up"), we already have a facility for doing that precisely and
accurately: catch IndexError. That catches out of bounds indicies and
nothing else[1], and it handles negative indicies correctly. list.get
can't be implemented much more efficiently than by using try
... except IndexError, and invoking it imposes attribute lookup and
function call overhead so I guess you net approximately nothing on
time, and a little bit of space. If you care so much about either
time or space, you'd implement inline, something like:
value = lst[index] if - (N := len(lst)) <= index < N else default
try ... except IndexError is TOOWTDI now, it's as readable as .get and
more readable than the inline version, so introducing list.get would
be redundant.
Second, I can see why people would want it (see my reply to MAL), I
just don't want it myself, and implementing your own *correctly* as a
function is trivial:
def get(container, subscript, default):
try:
return container[subscript]
except (IndexError, KeyError):
return default
It follows that I think dict.get is a YAGNI, at least since the
introduction of KeyError, and definitely now that we can write
y = mydict[x] if x in mydict else default
Footnotes:
[1] It turns out that slice bounds can't be out of bounds, they
simply get truncated, in the degenerate case to the empty slice.
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