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classification
Title: from __future__ import division breaks ad hoc numeric types
Type: behavior Stage:
Components: None Versions: Python 2.7
process
Status: closed Resolution: not a bug
Dependencies: Superseder:
Assigned To: Nosy List: benjamin.peterson, gumtree
Priority: normal Keywords:

Created on 2011-10-08 22:58 by gumtree, last changed 2022-04-11 14:57 by admin. This issue is now closed.

Messages (2)
msg145195 - (view) Author: Blair (gumtree) Date: 2011-10-08 22:58
I believe that the use of __future__.division may have unintended consequences with user types that define division.

The following fails:

	from __future__ import division

	class NumericType(object):
		def __init__(self,x):
			self.x = x

		def __div__(self,rhs):
			return self.x/rhs

	print NumericType(3.0) / 2.0

with the error message

  File "C:\proj_py\learning\future_bug\future.py", line 10, in <module>
    print NumericType(3.0) / 2.0
TypeError: unsupported operand type(s) for /: 'NumericType' and 'float'

Remove the line `from __future__ import division` and everything works fine.

I am using Python 2.7.2
msg145196 - (view) Author: Benjamin Peterson (benjamin.peterson) * (Python committer) Date: 2011-10-08 23:18
You have to implement __truediv__.
History
Date User Action Args
2022-04-11 14:57:22adminsetgithub: 57346
2011-10-08 23:18:00benjamin.petersonsetstatus: open -> closed

nosy: + benjamin.peterson
messages: + msg145196

resolution: not a bug
2011-10-08 22:58:36gumtreecreate