Here is my approach:

1. Treat regular expression as a finite state machine.
2. Draw states and transitions accordingly.
3. Eliminate intermediate states.

This kata has only a few states, which can be solved by pen and paper.

I've tested the same solution code of mine for Python 2.7.6 and Python 3.4.3 just now and both pass all final test cases. I think there is no issue if you aren't using version-specific stuff.

I am totally agreed with semiessessi. It's a shame to call this piece of **** best practice.

Python 3.4.3 is not supported, that must have been a bug with the allowed versions. 2.7 is now the only option for this challenge.

Same problem here...

"Do not use built in functions."

When will this be fixed? And still an issue after 7 months...

still an issue after 6 months...

Still an issue after 5 months...

Those two test cases do have the same code, but they have different input. Here is what the second test case looks like:

Test.assert_equals(whitespace(io123, "8\n6\n7\n"), "867")

This what I got when i submit.

File "", line 74     
   	Test.it("Testing ASCII85 encoding of %s" % `unit`)
                                            ^
SyntaxError: invalid syntax

Please fix this testcase for Python 3.4.3

I was stuck at input functionality test where the first two testcases have same Whitespace code and input, but expect different output:
Code："ssstntnttssstsntnttsssttntnttsssttntttssstsntttssstnttttnsttnsttnstnnn"
Input : "1","2","3"
Expect output 1 : "123"(passed)
Expect output 2 : "867"(failed)
My output : "123"
Language : Python

Did I miss something? Or there's something wrong with the testcases?