On Mon, 18 Jan 2010 16:43:25 +0100, superpollo wrote:
> hi:
>
> #!/usr/bin/env python
> data = "seq=123"
> name , value = data.split("=")
> print name
> print value
> if not name == "seq":
> print "DOES NOT PRINT OF COURSE..."
> if name is not "seq":
> print "WTF! WHY DOES IT PRINT?"
`is` is not an alternative spelling for `==`. `is` tests for object
identity, not equality. Unless you care about object identity, always use
equals.
>>> 'seq 1' is 'seq 1' # the SAME object is used twice
True
>>> s = "seq 1" # TWO objects are used
>>> t = "seq 1"
>>> s is t
False
Beware: Python caches strings that look like identifiers. This will
include "seq". So, purely as an implementation-specific detail, Python
will sometimes re-use the same string object, and sometimes not.
Do not use `is` when you are testing for equality.
By the way, instead of
not name == "seq"
you should write
name != "seq"
--
Steven
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