Message 348817 - Python tracker [proxy]

Message348817

Author	mrabarnett
Recipients	ezio.melotti, mrabarnett, serhiy.storchaka, yannvgn
Date	2019-07-31.17:23:32
SpamBayes Score	-1.0
Marked as misclassified	Yes
Message-id	<1564593812.49.0.157396144592.issue37723@roundup.psfhosted.org>
In-reply-to

Content
I've just had a look at _uniq, and the code surprises me. The obvious way to detect duplicates is with a set, but that requires the items to be hashable. Are they? Well, the first line of the function uses 'set', so they are. Why, then, isn't it using a set to detect the duplicates? How about this: def _uniq(items): newitems = [] seen = set() for item in items: if item not in seen: newitems.append(item) seen.add(item) return newitems

Content

I've just had a look at _uniq, and the code surprises me.

The obvious way to detect duplicates is with a set, but that requires the items to be hashable. Are they?

Well, the first line of the function uses 'set', so they are.

Why, then, isn't it using a set to detect the duplicates?

How about this:

def _uniq(items):
    newitems = []
    seen = set()
    for item in items:
        if item not in seen:
            newitems.append(item)
            seen.add(item)
    return newitems

History
Date	User	Action	Args
2019-07-31 17:23:32	mrabarnett	set	recipients: + mrabarnett, ezio.melotti, serhiy.storchaka, yannvgn
2019-07-31 17:23:32	mrabarnett	set	messageid: <1564593812.49.0.157396144592.issue37723@roundup.psfhosted.org>
2019-07-31 17:23:32	mrabarnett	link	issue37723 messages
2019-07-31 17:23:32	mrabarnett	create