How to change filetype association in the registry?

Question

first time posting in StackOverflow. :D I need my software to add a couple of things in the registry.

My program will use

Process.Star

Answer 1

Using Python:

EXT, EXT_TYPE = ".xyz", "XYZ file"
EXE_PATH = r"path\to\my\exe"

# %L is the long (full path) version of path
extCmd = '"%s" "%%L" %%*' % EXE_PATH

# Using assoc and ftype easier than editing registry!
assert os.system('assoc %s=%s' % (EXT, EXT_TYPE))==0
assert os.system('ftype %s=%s' % (EXT_TYPE, extCmd))==0

Associating an icon with the extension type:

import _winreg

try:
    ext = _winreg.OpenKey(_winreg.HKEY_CLASSES_ROOT, EXT_TYPE)
    _winreg.SetValue(ext, "DefaultIcon", _winreg.REG_SZ, ICON_PATH)
    _winreg.CloseKey(ext)
except WindowsError:
    print "Error associating icon"

Register the extension as an executable type (i.e. PATHEXT):

try:
    key = r'SYSTEM\CurrentControlSet\Control\Session Manager\Environment'

    reg = _winreg.ConnectRegistry( None, _winreg.HKEY_LOCAL_MACHINE )

    # get current value
    ext = _winreg.OpenKey(reg, key)
    pathext = _winreg.QueryValueEx(ext, 'PATHEXT')[0]

    if not EXT in pathext:
        _winreg.CloseKey(ext)

        # modify the current value            
        ext = _winreg.OpenKey(reg, key, 0, _winreg.KEY_ALL_ACCESS)
        pathext += ';' + EXT
        _winreg.SetValueEx(ext, 'PATHEXT', 0, _winreg.REG_SZ, pathext)
        _winreg.CloseKey(ext)

    _winreg.CloseKey(reg)

except WindowsError:
    print "Error adding to PATHEXT"

Additionally, to get PATHEXT recognised without logging in again you can update the environment: (thanks to Enthought for this)

def refreshEnvironment():        
    HWND_BROADCAST      = 0xFFFF
    WM_SETTINGCHANGE    = 0x001A
    SMTO_ABORTIFHUNG    = 0x0002
    sParam              = "Environment"

    import win32gui
    res1, res2          = win32gui.SendMessageTimeout(HWND_BROADCAST, WM_SETTINGCHANGE, 0, sParam, SMTO_ABORTIFHUNG, 100)