Providing the Microsoft Visual C runtime DLL

5. Providing the Microsoft Visual C runtime DLL

The Python interpreter was compiled using Microsoft Visual C, so your new program needs the Microsoft Visual C runtime DLL to run. If you have installed appropriate versions of Python or Visual Studio, then you will already have this DLL on your computer. If some of your users might not already have this DLL, then they will not be able to run your program. The methods you may use to solve this depend on the version of Python you are using:

5.1. Python 2.4 or 2.5

If you are using Python 2.4 or 2.5, then the DLL you need is called MSVCR71.dll. This DLL will probably already have been included in your dist directory, in which case you need do nothing more.

However, the copyright on this file is owned by Microsoft, and you need to check whether you have the legal right to redistribute it. If you have a copy of Visual Studio, check the file redist.txt provided within the installation to see whether you have redistribution rights for this DLL. Generally you have the right to redistribute it if you own a license for Microsoft Visual C++, but not if you use the Express Editions.

If you do not have the rights to redistribute MSVCR71.dll, then your users must install it for themselves, using the Microsoft Visual C++ 2005 Redistributable Package (vcredist_x86.exe).

Either you can instruct your users to download and run this themselves, or you could create an installer for your application (see Step 6 below), that includes vcredist_x86.exe (which is itself redistributable by anyone), and then run that as part of your application installation.

5.2. Python 2.6, 2.7, 3.0, 3.1

For Python 2.6, the DLL you need is called MSVCR90.dll. Py2exe is not able to automatically include this DLL in your dist directory, so you must provide it yourself.

To complicate things, there is more than one version of this DLL in existance, each with the same filename. You need the same version that the Python interpreter was compiled with, which is version 9.0.21022.8. Through the remainder of these instructions, hover your mouse over the dll file (or the vcredist_x86.exe installer executable) to confirm which version you've got. You'll need the vcredist_x86.exe that contains the Microsoft Visual C++ 2008 Redistributable Package published 29-11-2007, so not the VS2008 SP1 one (tested with Python 2.7.1).

As for older versions of Python, you need to check redist.txt within your Visual Studio installation to see whether you have the legal right to redistribute this DLL. If you do have these rights, then you have the option to bundle the C runtime DLL with you application. If you don't have the rights, then you must have your users run the redistributable C runtime installer on their machines.

5.2.1. Bundling the C runtime DLL

If you do have the rights to redistribute MSVCR90.dll, there should be a copy of it in your Visual Studio install, under VC\redist\x86\Microsoft.VC90.CRT. Since Visual Studio 2008, you can't just copy this DLL file - you also need the manifest file that you'll find there. The redist.txt file states that you must distribute all three dlls and the unmodified manifest file and it is a violation of the license agreement to distribute only one of the dlls without the others (though py2exe only needs MSVCR90.dll.) The pertinent passage from the redist.txt file is as follows:

• "For your convenience, we have provided the following folders for use when redistributing VC++ runtime files. Subject to the license terms for the software, you may redistribute the folder (unmodified) in the application local folder as a sub-folder with no change to the folder name. You may also redistribute all the files (*.dll and *.manifest) within a folder, listed below the folder for your convenience, as an entire set."

You must make py2exe copy the three dlls and the manifest file into your project's dist directory, in a subdirectory called 'Microsoft.VC90.CRT'. To achieve this, add a data_files option to your project's setup.py:

  from glob import glob
  data_files = [("Microsoft.VC90.CRT", glob(r'C:\Program Files\Microsoft Visual Studio 9.0\VC\redist\x86\Microsoft.VC90.CRT\*.*'))]
  setup(
    data_files=data_files,
    etc
  )

With this in place, running py2exe should put the files into your dist directory:

  dist
  |
  +-Microsoft.VC90.CRT
  | |
  | +-Microsoft.VC90.CRT.manifest
  | +-msvcm90.dll
  | +-msvcp90.dll
  | +-msvcr90.dll
  |
  |-etc

Now, simply copying the whole dist directory to your users machines should now allow your application to run, even on machines that don't have their own copy of the C++ runtime.

Note that this method of including the C runtime is used by several Visual C++ applications - if you search your Program Files folder for msvcr90.dll, you may find several applications that have this DLL and the associated manifest bundled alongside their executable like this.

Also note that despite all the above, py2exe will complain that it cannot find MSVCP90.dll. You must edit your setup.py to add the path to the dlls to the sys.path, e.g.

    sys.path.append("C:\\Program Files\\Microsoft Visual Studio 9.0\\VC\\redist\\x86\\Microsoft.VC90.CRT")

5.2.1.1 win32ui special case

win32ui needs MFC DLLs to run .exe, see Py2exeAndWin32ui for extra informations

5.2.2. Running the redistributable C runtime installer

If you don't have rights to redistribute MSVCR90.dll, then your users may install it on their machine by running the Microsoft Visual C++ 2008 Redistributable Package (vcredist_x86.exe). It is important not to use the SP1 version of this installer, which contains the wrong version of MSVCR90.dll.

Either you can instruct your users to download and run this themselves, or you could create an installer for your application (see step 6 below), that includes vcredist_x86.exe (which is itself redistributable by anyone), and then run that as part of your application installation.

The installer puts a copy of the DLLs in the directory C:\WINDOWS\WinSxS (XP), inside subdirectories with mangled names. The manifest file is in the 'Manifests' subdirectory, again this will have a mangled filename. You can still discern the text 'Microsoft.VC90.CRT' and '9.0.21022.8' within the mangled file and directory names, to find the files. It is possible to take a copy of these files and remove the filename mangling, to embed them in your application as described in 5.2.1.