when you recently deployed a project, the PIP install requirements required a pygraphviz package. This package is for graphical data.
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is the associated error message as shown below.

error: Microsoft Visual C++ 10.0 is required. Get it with "Microsoft Windows SDK 7.1": www.microsoft.com/download/details.aspx?id=8279

  ----------------------------------------
  Failed building wheel for pygraphviz
  Running setup.py clean for pygraphviz
Successfully built dominate Flask-Bootstrap flask-nav Flask-Uploads itsdangerous MarkupSafe visitor
Failed to build pygraphviz
Installing collected packages: appdirs, chardet, click, dominate, MarkupSafe, Jinja2, itsdangerous, Werkzeug, Flask, visitor, Flask-Bootstrap, Flask-Login, flask-nav, Flask-Uploads, WTForms, Flask-WTF, gunicorn, iso8601, numpy, pyparsing, six, packaging, pytz, requests, decorator, networkx, graphviz, pygraphviz
  Running setup.py install for pygraphviz ... error
    Complete output from command f:\fiat_dev\venv\scripts\python.exe -u -c "import setuptools, tokenize;__file__='C:\\Users\\JIANGM~1.FNS\\AppData\\Local\\Temp\\pip-install-b3cfvse8\\pygraphviz\\setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record C:\Users\JIANGM~1.FNS\AppData\Local\Temp\pip-record-h2160l90\install-record.txt --single-version-externally-managed --compile --install-headers f:\fiat_dev\venv\include\site\python3.4\pygraphviz:
	...
    running build_ext
    building 'pygraphviz._graphviz' extension
    error: Microsoft Visual C++ 10.0 is required. Get it with "Microsoft Windows SDK 7.1": www.microsoft.com/download/details.aspx?id=8279

    ----------------------------------------
Command "f:\fiat_dev\venv\scripts\python.exe -u -c "import setuptools, tokenize;__file__='C:\\Users\\JIANGM~1.FNS\\AppData\\Local\\Temp\\pip-install-b3cfvse8\\pygraphviz\\setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record C:\Users\JIANGM~1.FNS\AppData\Local\Temp\pip-record-h2160l90\install-record.txt --single-version-externally-managed --compile --install-headers f:\fiat_dev\venv\include\site\python3.4\pygraphviz" failed with error code 1 in C:\Users\JIANGM~1.FNS\AppData\Local\Temp\pip-install-b3cfvse8\pygraphviz\

in normal fashion, I started Posting this error message to Google. Found some so-called solutions, including pyGraphviz’s Github community, and other blog posts. The solution:
1. Let you install graphviz, then set the environment variable. Then specify at installation time a parameter such as Pip’s inlude path
2. Let you install a 32-bit python, then go to 1, recompile and install pygraphviz
3. Just get out of Windows Binaries for Python Extension Packages.
I’ve tried all of the above solutions. However, when I was compiling, there were a lot of c compilation errors. Format conversion errors and so on. doesn’t solve the real problem . I feel suspicious, these posts on the Net clearly say that doing so can solve ah!

when I received a useful message saying that pygraphviz does not support python3.4 or above . So I reinstalled Python 3.4 and changed the system’s Python environment variable. When I re-installed PIP Install Pygraphviz-xxx-.whl in the CMD, I was notified that the installation was successful.
but for this project I used vitrualenv to manage the packages it needed. I just wrapped this in the system Python library. So I activate the current venv,
and run PIP install pygraphviz-xxx-.whl again, a familiar error message appears:

(venv) F:\pygraphviz-1.3.1>pip install pygraphviz-1.3.1-cp34-none-win_amd64.whl
pygraphviz-1.3.1-cp34-none-win_amd64.whl is not a supported wheel on this platform.
You are using pip version 10.0.1, however version 18.0 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.

wait, didn’t you just install it?What’s the problem?
after some thinking, I found that the virtual python environment built in venv was set up a week ago. At that time, the python version of the system was 3.5.
, so the python version in this virtual environment was also 3.5. So the installation failed. To prove my point, I deleted Venv, re-opened a CMD, and reinstalled a virtual environment.
when I type PIP install pygraphviz-xxx-.whl again, the command line indicates that the installation was successful.