Append a user-friendly message after 'Unable to find vcvarsall.bat' explaining how to fix the problem

[hickford]

There are millions of Python developers on Windows. They would like to use libraries. If they succeed in installing pip, this is typically their first experience with it:

$ pip install numpy

blah blah blah

Error: Unable to find vcvarsall.bat

And often their last. That cryptic message "Unable to find vcvarsall.bat" is meaningless to most people, and sends users on a fool's errand (trying to download a file called vcvarsall.bat).

Ideally, package management would work out the box but if that can't be done, it would be courteous to make the error more user-friendly with instructions how to actually fix the problem. I suggest

Error: Installing this package requires a C compiler, which you do not have. To fix this error, install and configure a C compiler following http://stackoverflow.com/q/2817869/284795

---

For comparison, Ruby ships with a package manager, Gem. If a user tries to install a package with C extensions but doesn't have a C compiler installed, they are given this user-friendly message:

Please update your PATH to include build tools or download the DevKit from 'http://rubyinstaller.org/downloads' and follow the instructions at 'http://github.com/oneclick/rubyinstaller/wiki/Development-Kit'

[BenjaminSchaaf]

I'd like to bump this, it's really annoying and causes great pain to those that just want to use python without having to depend on a C compiler

[pfmoore]

That message comes from Python's distutils. You need to file a request at http://bugs.python.org if you want this changed.

[hickford]

Reported upstream at Python.org http://bugs.python.org/issue2943 please vote for it. If you feel strongly, make a python.org account and comment.

[srw]

The message appears even if you have a C compiler...

Here I found the best answer: http://stackoverflow.com/questions/2667069/cannot-find-vcvarsall-bat-when-running-a-python-script

Python is not recognizing newer versions of Visual Studio

[jerusalemprogrammer]

Hi,
I have stumbled across this issue now tonight trying myself to install the NumPy package - I still cannot find a clear answer.

Does anyone know how I can get past this error so that I can install only NumPy and not have to download Enthought or Anaconda packages?

Thanks.

[hickford]

@jerusalemprogrammer the easiest way to install Numpy on vanilla Python is the Windows installers at http://www.lfd.uci.edu/~gohlke/pythonlibs/

[jerusalemprogrammer]

Hi Mr. Hickford,

Thanks for the prompt reply.

I have seen these referred to - but am suspicious of third-party software
that is not from large established, trusted group.

Are there any other solutions?

I read that Python needed C compiler, so it was recommended to download
Visual Studio - so I did, but this didn't work.

Do you know of any other solution?

Thanks.

kindest regards,

On Tue, Dec 23, 2014 at 11:57 AM, Matt Hickford notifications@github.com
wrote:

@jerusalemprogrammer https://github.com/jerusalemprogrammer the easiest
way to install Numpy on vanilla Python is the Windows installers at
http://www.lfd.uci.edu/~gohlke/pythonlibs/

—
Reply to this email directly or view it on GitHub
#942 (comment).

[lrq3000]

Yes there is a solution:

1. install Microsoft Visual C++ Compiler for Python from http://www.microsoft.com/en-us/download/details.aspx?id=44266
2. Enter MSVC for Python command prompt
3. SET DISTUTILS_USE_SDK=1
4. SET MSSdk=1
5. you can then build your C extensions: python.exe setup.py ...

Steps 2 to 4 must be reproduced everytime before building your C extensions. This is because of an issue with the VCForPython27.msi which install the header files and vcvarsall.bat in folders of a different layout than the VS2008 SDK and thus confuse the compiler detection of distutils. This will get fixed in setuptools in Python 2.7.10.

Bug report and workaround by Gregory Szorc:
http://bugs.python.org/issue23246

[MikeTam1021]

Irq3000... your directions are not simple and clear enough for me. Enter MSVC where? Where and how am I doing these things?... I downloaded that, I am still without a clue.

[lrq3000]

@MikeTam1021 More up to date info can now be found here:
https://github.com/cython/cython/wiki/CythonExtensionsOnWindows

In particular, you can just import setuptools instead of distutils and this should correctly load the VCForPython27 compiler.

Else if you really want to use the commands I described above, you just have to set them in a console, so just run cmd.exe and type the commands there.

[MikeTam1021]

thanks Irq3000, that worked