So I contacted the Unicode Technical Committee about the issue and received a promptly received a response back. They pointed that the ZWSP was, once upon a time considered white space but that was changed in Unicode 4.0.1

http://www.unicode.org/review/resolved-pri.html#pri21

One particular comment worth noting: "... for historical reasons the general category is still Zs (Space Separator)".

Perhaps this ticket can be changed to a feature request? In addition to stripping out whitespace, it is useful to remove any non-printable characters from a string (or know if a string contains any non-printable characters).

Perhaps a boolean keyword parameter, "control_chars" could be added to isspace and strip? Thus:

>>> u' \t\r\n\u200B'.isspace(control_chars=True)
True