mk wrote in news:mailman.923.1259070092.2873.python-l...@python.org in comp.lang.python:
> MRAB wrote: >> In what way is it counterintuitive? In 'pythonic' the conditions are >> simpler, less work is being done, therefore it's faster. > > But the pythonic condition is more general: nonevar or zerovar can be > '', 0, or None. So I thought it was more work for interpreter to compare > those, while I thought that "is not None" is translated to one, more > low-level and faster action. Apparently not. > > As Rob pointed out (thanks): > > 11 31 LOAD_FAST 0 (nonevar) > 34 JUMP_IF_FALSE 4 (to 41) > > I'm no good at py compiler or implementation internals and so I have no > idea what bytecode "JUMP_IF_FALSE" is actually doing. IIUC it implements: http://docs.python.org/3.1/reference/expressions.html#boolean-operations "In the context of Boolean operations, and also when expressions are used by control flow statements, the following values are interpreted as false: False, None, numeric zero of all types, and empty strings and containers (including strings, tuples, lists, dictionaries, sets and frozensets). All other values are interpreted as true. User-defined objects can customize their truth value by providing a __bool__() method." In particular its implementing "... Boolean operation ... used by control flow ...", all in one handy op code. Rob. -- http://mail.python.org/mailman/listinfo/python-list
