How do I find the Windows common application data folder using Python?

Question

I would like my application to store some data for access by all users. Using Python, how can I find where the data should go?

Answer 1

Since SHGetFolderPath is deprecated, you can also use SHGetKnownFolderPath in Vista and newer. This also lets you look up more paths than SHGetFolderPath will. Here's a stripped-down example (full code available on Gist):

import ctypes, sys
from ctypes import windll, wintypes
from uuid import UUID

class GUID(ctypes.Structure):   # [1]
    _fields_ = [
        ("Data1", wintypes.DWORD),
        ("Data2", wintypes.WORD),
        ("Data3", wintypes.WORD),
        ("Data4", wintypes.BYTE * 8)
    ] 

    def __init__(self, uuid_):
        ctypes.Structure.__init__(self)
        self.Data1, self.Data2, self.Data3, self.Data4[0], self.Data4[1], rest = uuid_.fields
        for i in range(2, 8):
            self.Data4[i] = rest>>(8 - i - 1)*8 & 0xff

class FOLDERID:     # [2]
    LocalAppData            = UUID('{F1B32785-6FBA-4FCF-9D55-7B8E7F157091}')
    LocalAppDataLow         = UUID('{A520A1A4-1780-4FF6-BD18-167343C5AF16}')
    RoamingAppData          = UUID('{3EB685DB-65F9-4CF6-A03A-E3EF65729F3D}')

class UserHandle:   # [3]
    current = wintypes.HANDLE(0)
    common  = wintypes.HANDLE(-1)

_CoTaskMemFree = windll.ole32.CoTaskMemFree     # [4]
_CoTaskMemFree.restype= None
_CoTaskMemFree.argtypes = [ctypes.c_void_p]

_SHGetKnownFolderPath = windll.shell32.SHGetKnownFolderPath     # [5] [3]
_SHGetKnownFolderPath.argtypes = [
    ctypes.POINTER(GUID), wintypes.DWORD, wintypes.HANDLE, ctypes.POINTER(ctypes.c_wchar_p)
] 

class PathNotFoundException(Exception): pass

def get_path(folderid, user_handle=UserHandle.common):
    fid = GUID(folderid) 
    pPath = ctypes.c_wchar_p()
    S_OK = 0
    if _SHGetKnownFolderPath(ctypes.byref(fid), 0, user_handle, ctypes.byref(pPath)) != S_OK:
        raise PathNotFoundException()
    path = pPath.value
    _CoTaskMemFree(pPath)
    return path

common_data_folder = get_path(FOLDERID.RoamingAppData)

# [1] http://msdn.microsoft.com/en-us/library/windows/desktop/aa373931.aspx
# [2] http://msdn.microsoft.com/en-us/library/windows/desktop/dd378457.aspx
# [3] http://msdn.microsoft.com/en-us/library/windows/desktop/bb762188.aspx
# [4] http://msdn.microsoft.com/en-us/library/windows/desktop/ms680722.aspx
# [5] http://www.themacaque.com/?p=954