Patches item #1675423, was opened at 2007-03-07 03:03 Message generated for change (Tracker Item Submitted) made by Item Submitter You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=305470&aid=1675423&group_id=5470
Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Core (C code) Group: Python 2.6 Status: Open Resolution: None Priority: 5 Private: No Submitted By: Mark Dickinson (marketdickinson) Assigned to: Nobody/Anonymous (nobody) Summary: Make PyComplex_AsCComplex use __complex__ Initial Comment: The functions in the math module have the (pleasantly) surprising and apparently undocumented property that they'll accept not just floats, but any Python object having a float method: >>> class test1(object): ... def __float__(self): ... return 3. ... >>> from math import sqrt >>> sqrt(test1()) 1.7320508075688772 Based on this, one might expect the functions in the complex math module cmath to have the same property with respect to __complex__. But this isn't so: >>> class test2(object): ... def __complex__(self): ... return -3 + 0j ... >>> from cmath import sqrt as csqrt >>> csqrt(test2()) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: a float is required The real surprise is that the cmath functions *will* call the __float__ method, if it's available: >>> csqrt(test1()) (1.7320508075688772+0j) This patch expands the PyComplex_AsCComplex method so that it looks for a __complex__ method before looking for the __float__ method. This `fixes' the above behaviour. Should it be a documented feature that the math functions will make use of __float__? If so, and if the patched behaviour seems desirable, I'll add suitable tests to test_math and test_cmath. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=305470&aid=1675423&group_id=5470 _______________________________________________ Patches mailing list Patches@python.org http://mail.python.org/mailman/listinfo/patches
