On Mon, Dec 17, 2012 at 3:55 AM, Alan Gauld <alan.ga...@btinternet.com> wrote: > > So you are right, there is an inconsistency between how int() converts > floating point numbers and how it converts strings. Even stranger since the > underlying atoi() C function appears to handle float strings quite > happily...
If you're using strtol in C it's up to you how to interpret an incomplete conversion due to an out-of-range number or bad literal for the given base. Python, on the other hand, automatically switches the type for big integers to a multiprecision long (2.x long) and raises ValueError for bad literals. Where you go from there is up to you. BTW, 2.x int() isn't using the libc atoi or strtol/strtoul functions. It has its own implementation in mystrtoul.c. PyOS_strtol wraps the main workhorse PyOS_strtoul (unsigned): http://hg.python.org/cpython/file/70274d53c1dd/Python/mystrtoul.c#l80 The conversion loop proceeds up to the first non-base character, as defined by the table _PyLong_DigitValue in longobject.c: http://hg.python.org/cpython/file/70274d53c1dd/Objects/longobject.c#l1604 A pointer to the last scanned character is set. In PyInt_FromString, if this points to the first character, or the previous character isn't alphanumeric, or removing trailing whitespace starting from this point doesn't end on a NUL terminator (e.g. *end == '.'), then the conversion raises a ValueError. See lines 364-383 in intobject.c: http://hg.python.org/cpython/file/70274d53c1dd/Objects/intobject.c#l340 _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
