On 04.01.14 13:58, Serhiy Storchaka wrote:
Should implicit converting an instance of int, float, complex, str, bytes, etc subclasses to call appropriate special method __int__ (or __index__), __float__, __complex__, __str__, __bytes__, etc? Currently explicit converting calls these methods, but implicit converting doesn't.
class I(int): ... def __int__(self): return 42 ... def __index__(self): return 43 ... class F(float): ... def __float__(self): return 42.0 ... class S(str): ... def __str__(self): return '*' ... int(I(65)) 42 float(F(65)) 42.0 str(S('A')) '*' chr(I(65)) 'A' import cmath; cmath.rect(F(65), 0) (65+0j) ord(S('A')) 65
Issue17576 [1] proposes to call special methods for implicit converting. I have doubts about this.
Note that for explicit conversion this was implemented a long time ago. See this ancient thread about str/unicode subclasses and __str__/__unicode__: https://mail.python.org/pipermail/python-dev/2005-January/051175.html And this bug report: http://bugs.python.org/issue1109424
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Servus, Walter