What happened to ifilter?

Question

In comparing documentation for itertools between Python 2 and 3, I noticed ifilter, imap, izip are missing from Python 3. I suspect this is because many builtin keywords have been converted to generators and replaced former keywords, but it is unclear in this case.

Is it true ifilter, imap, izip are now equivalent to filter, map, zip in Python 3? If not, where can I find rationales for why certain methods were removed from current itertools?

Answer 1

Python 2.3 introduced the itertools module, which defined variants of the global zip(), map(), and filter() functions that returned iterators instead of lists. In Python 3, those global functions return iterators, so those functions in the itertools module have been eliminated.

• Instead of itertools.izip(), just use the global zip() function.
• Instead of itertools.imap(), just use map().
• itertools.ifilter() becomes filter().
• The itertools module still exists in Python 3, it just doesn’t have the functions that have migrated to the global namespace. The 2to3 script is smart enough to remove the specific imports that no longer exist, while leaving other imports intact.

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