Caveat: Hopefully my chaining of operators there didn't mislead, that was unintended. I think most of what I said still holds, if not all.
-Don On Aug 2, 9:14 am, mda_ <donmorri...@gmail.com> wrote: > SageDevs, > > In the interest of "gotchas", please consider the following: > > The built-in str, and the module string are different, though both > return type str according to type(). > > Example: > > d...@dv9000-laptop:~$ python2.6 > Python 2.6.4 (r264:75706, Dec 7 2009, 18:43:55) > [GCC 4.4.1] on linux2 > Type "help", "copyright", "credits" or "license" for more information.>>> > from copy import copy,deepcopy > >>> import string > >>> a = '12 3 four five six' > >>> a is copy(a) is deepcopy(a) > True > >>> a == copy(a) == deepcopy(a) > True > >>> b = string.lower(a) > >>> a > > '12 3 four five six' > > > > > > >>> a is b > False > >>> a == b > True > >>> type(a) > <type 'str'> > >>> type(b) > <type 'str'> > >>> c = copy(a) > >>> c is a > True > >>> d = deepcopy(a) > >>> d is a > True > >>> hash(a) == hash(b) > True > >>> id(a) == id(b) > False > >>> id(a) == id(c) == id(d) > True > >>> id(a) is id(c) is id(d) > False > >>> hash(a) == hash(b) == hash(c) == hash(d) > True > >>> hash(a) is hash(b) is hash(c) is hash(d) > False > >>> type(a) == type(b) == type(c) == type(d) > True > >>> type(a) is type(b) is type(c) is type(d) > True > > So, I think the take home message is that the keyword "is" is fragile > in some cases. Also, the return value of type() is misleading. > > http://docs.python.org/release/2.6.5/reference/lexical_analysis.html#... > > Cheers, > Don -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
