Hacker News Reader

Comment by tdhz77 | Hacker News Reader

Ok, context is required here.

try { int i = 0; while(true){ someArray[i]; i++; } } catch (IndexOutOfBoundsException ex) { //done }

That particular piece of code is too verbose and I believe will not even be particularly more efficient (even for very large arrays); BUT, the idea behind it, i.e., recklessly loop and just catch the exception is the most idiomatic way of both looping over collections and checking if one item exists in Visual Basic. It is, in fact, the most efficient general (works for all kinds of collections) way to check for "item x is in collection C" both in VB and python.

A few simple timings tell me this isn't actually fast in Python for finding an item in a list, compared to a bounded loop, (and, since I was curious, neither is a sentinel approach where you insert the expected item at the end of the given list), I guess CPython just heavily optimizes range-for loops, and maybe this was true in an old version of it.

(Yes, list.index exists. I know. Thank you.)

That is why I put the word "general"; C could be a dict, etc. I know that there are better ways for specific types, but the following code is a snippet that works for fast prototyping and I have found it to be idiomatic in VB for collections (but I do very occasional VB, less than once a year).

    # pythonic pseudocode
    def exists(x, C):
        try:
           C[x]
        except:
           # could be more specific
           # IndexError, KeyError, etc...         
           return False
        return True

I mean... That's so bad it's almost good?

How did this pass code review though?

Reply on news.ycombinator.com