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| From | Ned Batchelder <ned@nedbatchelder.com> |
| Subject | Re: __index__ |
| Date | Sat, 01 Nov 2014 13:11:25 -0400 |
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On 11/1/14 12:56 PM, duncan smith wrote: > Hello, > I have a Bloom filter class and want to (partially) serialize > instances using hex() or oct(). Instances are mutable, so I can't > inherit from long. I thought I'd found the answer when I came across > __index__, > https://docs.python.org/2/reference/datamodel.html#object.__index__. But > it doesn't seem to work as I expected it to. > > >>>> class MyClass(object): > def __init__(self): > self.val = 7 > def __index__(self): > return self.val > > >>>> x = MyClass() >>>> oct(x) > > Traceback (most recent call last): > File "<pyshell#76>", line 1, in <module> > oct(x) > TypeError: oct() argument can't be converted to oct >>>> oct(x.__index__()) > '07' >>>> > > > Can someone please explain why my thinking is wrong on this? TIA. Just above your link in the docs is __oct__ and __hex__, which are used to implement oct() and hex(): https://docs.python.org/2/reference/datamodel.html#object.__oct__ That said, I would simply add a .hex() method on the class. I would never expect a complex thing like a Bloom filter to be turned into useful hex with the hex() builtin. For example, when making an MD5 hash, you use the md5.hexdigest() method, not hex(md5). -- Ned Batchelder, http://nedbatchelder.com
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__index__ duncan smith <buzzard@invalid.invalid> - 2014-11-01 16:56 +0000
Re: __index__ Ned Batchelder <ned@nedbatchelder.com> - 2014-11-01 13:11 -0400
Re: __index__ duncan smith <buzzard@invalid.invalid> - 2014-11-01 17:15 +0000
Re: __index__ Ethan Furman <ethan@stoneleaf.us> - 2014-11-01 11:29 -0700
Re: __index__ duncan smith <buzzard@invalid.invalid> - 2014-11-01 19:41 +0000
Re: __index__ Ethan Furman <ethan@stoneleaf.us> - 2014-11-01 13:00 -0700
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