How do I get ftype & assoc to match Windows Explorer?

I changed the association to use upon launching a .py file, via Windows Explorer:

1. Tools -> Folders -> File types.
2. Then browse to .py.
3. Change the association to Wordpad.

Now when I type the name of a py file in the command line, Wordpad opens it.

But assoc and ftype in the command line still return the following:

C:\> assoc .py
.py = Python.File

C:\> ftype Python.File
Python.File = "C:\Program\Python27\python.exe" "%1" %*

How come the association is working, but assoc and ftype are not aware of it?

I did restart the prompt.

More info from my registry:

HKEY_CLASSES_ROOT\.py
= Python.File

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.py\Application
= wordpad.exe

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.py\OpenWithProgids\Python.File
= 

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\.py\(Standard)
= Python.File

More registry:

HKEY_CLASSES_ROOT\Applications\python.exe\shell\open\command\(Standard)
= "C:\Program\Python27\python.exe" "%1" %*`

I suppose this is what is showing up in ftype Python.File. But it does not seem to get used.

(I am doing this for testing, so I can eventually choose my default version of Python easily).

Solution 1:

Depending on how you call a file will depend on what verb is used. The verb you use determines what Windows will do with it. The standard verbs are Open, Edit, Print, Play, and Preview. However, it is possible to create your own verbs. The most commonly added verb is the Open With family (including OpenWithProgIDs), which add that little context sub-menu under "Open With" to give you possible alternatives. If you install Paint.NET, for example, and then right-click a .jpg file, you'll see the Open With entry expands to a submenu that lists Paint.NET, Paint, and whatever Microsoft called the picture viewer for your version of Windows.

Additionally, what Unsigned Code Labs said is very important. When you're debugging classes, you need to look at HKLM\Software\Classes\ and HKCU\Software\Classes. HKCR is very useful for querying the system, but not so good for finding out why it's misbehaving.

I did a little testing on my Windows 7 system with procmon.exe, and the assoc and ftype commands appear to try to write directly to HKCR, and the system apparently interprets that as writing to HKLM. My current account is a member of the admin group, but UAC is enabled. I got access denied when I tried assoc .mytest=MyTest.File.

Oddly, if I create an association by right-clicking a file called test.mytest and associating it with Notepad, neither assoc nor ftype sees this association. The association is definitely there in HKCU and HKCR. I haven't tried rebooting, however.

Solution 2:

i don't know how can you make the match between registry and what appears in ftype and assoc. To me and as i see to you as well the ftype and assoc command are useless. What i do to change the default program for a given extension in a programatic way(vs the standard and more simple way using explorer) is modify this registry key

HKCU:\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.TheExtensionYouWantToModify\UserChoice\ProgID

For example, if i want to open my mp3s with mplayer i put in

HKCU:\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.mp3\UserChoice\ProgID 

the value of "mplayerc.mp3"

What are the complication of doing this: first you need to know valids ProgIDs(use ftype), and second you need write access to that hive. Windows automatically put a deny ACL for the UserChoice key, so you need to find a way to remove that deny rule in order to get the write access. I use the program subinacl, that you could download from here http://www.microsoft.com/downloads/en/details.aspx?FamilyID=e8ba3e56-d8fe-4a91-93cf-ed6985e3927b&displaylang=en to modify the permissions. Also you could use the 3rd party program SetACL. I recomend the first because the syntax is a lot more simple.

Solution 3:

Microsoft have changed how this works from Windows 8 onward. It is no longer possible to edit the registry to change this. To quote Microsoft:

In Pre-Win 8, apps could set the default handler for a file type/protocol by manipulating the registry, this means you could easily have a script or a group policy manipulating the registry. However In Win 8, the registry changes are verified by a hash (unique per user and app) that detects tampering by apps. In the absence of a valid hash, we ignore the default in the registry.

The way Microsoft expect you to change this now is with an xml file which is implemented through Group Policy. Instructions here.

Thankfully Christoph Kolbicz has reverse engineered the hashing algorithm and created a tool called SetUserFTA to set the file type association. Unfortunately it is closed source.

Solution 4:

Explorer (the Windows shell) always gives preference to the application specified in the vendor key which is specified under the extension's default value. (In your case .py is the extension, Python.File is the vendor key.)

ftype and assoc may read their values from other areas, I do not know for sure. Thats just how Explorer does it.

EDIT: This page may be of interest to you: MSDN - File Types

Especially this:

The HKEY_CLASSES_ROOT subtree is a view formed by merging HKEY_CURRENT_USER\Software\Classes and HKEY_LOCAL_MACHINE\Software\Classes.

Perhaps this is where the different parts of Windows clash, if there is a "default" association in HKEY_LOCAL_MACHINE, that is getting overridden by the one you defined on your account (which would then be stored in HKEY_CURRENT_USER).