Hello,

Several string methods avoid allocating a new string when the operation result is trivially the same as one of the parameters (e.g. replacing a non-existing substring). However, split() does not exhibit this optimization, it always constructs a new string even if no splitting occurs:

$ python
Python 2.5 (r25:51908, Oct  6 2006, 15:22:41) 
[GCC 4.1.2 20060928 (prerelease) (Ubuntu 4.1.1-13ubuntu4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> s = "abcde" * 2
>>> id(s)
3084139400L
>>> id(str(s))
3084139400L
>>> id("" + s)
3084139400L
>>> id(s.strip())
3084139400L
>>> id(s.replace("g", "h"))
3084139400L
>>> [id(x) for x in s.partition("h")]
[3084139400L, 3084271768L, 3084271768L]
>>> [id(x) for x in s.split("h")]
[3084139360L]