[Python-Dev] getitem & slice question (original) (raw)

Tim Peters tim.one@comcast.net
Fri, 15 Mar 2002 01:47:42 -0500

[Skip Montanaro]

I checked in what I thought was a fix for calendar.py and testcalendar.py, then realized it didn't handle slices.

Why does that matter? calendar.all doesn't export _localized_name or any of the gimmicks built from it, so it's purely an internal issue, and the internals never need slices here (granted that day_name etc are poorly named for module privates -- or perhaps the all list and the docs are in error).

I've never dealt with getitem and slices before. Would someone try out this modified version of calendar.localizedname and let me know what I'm doing wrong?

class localizedname: def init(self, format, len): self.data = [] for i in range(len): self.data.append(strftime(format, (i,)*9).capitalize()) # months are one-based - match 2.1 behavior if format == '%b': self.data[0] = " " elif format == '%B': self.data[0] = ""

Now this changes the current semantics in a major way: if you're going to precompute all the values, construct plain tuples instead and be done with it. I assume that whoever patched this to begin with deliberately recomputed localized values on each dynamic reference so that they would respond appropriately to dynamic locale changes.

def getitem(self, item): if type(item) is types.SliceType: return self.data[item.start:item.stop] return self.data[item]

def len(self): return len(self.data) For example, try something like calendar.monthabbr[-20:] Also, should I worry about the slice's step attribute?

To both, I don't think you should be changing this code to do static precomputation at all. But, if we must, toss the class and build plain tuples instead, e.g.

day_name = tuple([strftime('%A', (i,)*9) for i in range(7)])

In the static case, trying to build a class that emulates a tuple is pointless.