Corectly convert from %PATH%=c:\\X; "c:\\a; b" TO ['c:\\X', 'c:\\a; b']

[Michael Spencer]

chirayuk wrote:

> 
> However, I just realized that the following is also a valid PATH in
> windows.

> 
> PATH=c:\A"\B;C"\D;c:\program files\xyz"
> (The quotes do not need to cover the entire path)

Too bad!  What a crazy format!
> 
> So here is my handcrafted solution.
> 
> def WinPathList_to_PyList (pathList):
>     pIter = iter(pathList.split(';'))
>     OddNumOfQuotes = lambda x: x.count('"') % 2 == 1
>     def Accumulate (p):
>         bAcc, acc = OddNumOfQuotes(p), [p]
>         while bAcc:
>             p = pIter.next ()
>             acc.append (p)
>             bAcc = not OddNumOfQuotes (p)
>         return "".join (acc).replace('"','')
>     return [q for q in [Accumulate (p) for p in pIter] if q]
> 
Does it work?

I get:
  >>> test2 = r'c:\A"\B;C"\D;c:\program files\xyz"'
  >>> WinPathList_to_PyList(test2)
  Traceback (most recent call last):
    File "<input>", line 1, in ?
    File "pathsplit", line 31, in WinPathList_to_PyList
    File "pathsplit", line 27, in Accumulate
  StopIteration
  >>>

Also, on the old test case, I get:
  >>> WinPathList_to_PyList("""\"c:\\A;B";c:\\D;""")
  ['c:\\AB', 'c:\\D']
  >>>

Should the ';' within the quotes be removed?

> 
> So now I need to check if the os is windows.
> 
> Wishful thinking: It would be nice if something like this (taking care
> of the cases for other OS's) made it into the standard library - the
> interpreter must already be doing it.
> 
This sort of 'stateful' splitting is a somewhat common task.  If you're feeling 
creative, you could write itertools.splitby(iterable, separator_func)

This would be a sister function to itertools.groupby (and possible derive from 
its implementation).  separator_func is a callable that returns True if the item 
is a separator, False otherwise.

splitby would return an iterator of sub-iterators (like groupby) defined by the 
items between split points

You could then implement parsing of crazy source like your PATH variable by 
implementing a stateful separator_func

Michael