python命令行安装graphviz、pygraphviz

1、
demo>pip install pygraphviz
报错Using legacy ‘setup.py install’ for pygraphviz, since package ‘wheel’ is not installed.
Installing collected packages: pygraphviz
Running setup.py install for pygraphviz … error

解决方法
pip install --user --force-reinstall pip
pip install wheel
pip install graphviz
pip install graphviz

2、
安装pygraphviz
是unofficial的包，只能从网上下载再安装

https://www.lfd.uci.edu/~gohlke/pythonlibs/

根据自己的python版本选择，不然会出现下面这个错误
pip install pygraphviz-1.6-cp39-cp39-win_amd64.whl
ERROR: pygraphviz-1.6-cp39-cp39-win_amd64.whl is not a supported wheel on this platform.
这样就对了：
D:\B毕业设计\demo>pip install pygraphviz-1.6-cp37-cp37m-win_amd64.whl
Processing d:\b毕业设计\demo\pygraphviz-1.6-cp37-cp37m-win_amd64.whl
Installing collected packages: pygraphviz
Successfully installed pygraphviz-1.6
3、
然而一运行代码，报错了，什么垃圾玩意，先把错误放这
graph has {nx.number_of_nodes(G)} nodes with {nx.number_of_edges(G)} edges
1 connected components
Traceback (most recent call last):
File “C:\Users\dell\software\python37\lib\site-packages\pygraphviz\agraph.py”, line 1345, in _get_prog
runprog = self._which(prog)
File “C:\Users\dell\software\python37\lib\site-packages\pygraphviz\agraph.py”, line 1595, in _which
raise ValueError(“No prog %s in path.” % name)
ValueError: No prog twopi in path.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File “D:/B毕业设计/demo/.idea/inspectionProfiles/test3Graphs.py”, line 44, in
pos = graphviz_layout(G, prog=“twopi”, root=0)
File “C:\Users\dell\software\python37\lib\site-packages\networkx\drawing\nx_agraph.py”, line 237, in graphviz_layout
return pygraphviz_layout(G, prog=prog, root=root, args=args)
File “C:\Users\dell\software\python37\lib\site-packages\networkx\drawing\nx_agraph.py”, line 285, in pygraphviz_layout
A.layout(prog=prog, args=args)
File “C:\Users\dell\software\python37\lib\site-packages\pygraphviz\agraph.py”, line 1422, in layout
data = self._run_prog(prog, " “.join([args, “-T”, fmt]))
File “C:\Users\dell\software\python37\lib\site-packages\pygraphviz\agraph.py”, line 1360, in _run_prog
runprog = r’”%s"’ % self._get_prog(prog)
File “C:\Users\dell\software\python37\lib\site-packages\pygraphviz\agraph.py”, line 1347, in _get_prog
raise ValueError(“Program %s not found in path.” % prog)
ValueError: Program twopi not found in path.
解决方案
http://www.graphviz.org/
还要在Windows里下载一个graphviz, 下载安装即可，安装过程中勾选添加path的选项，然后打开cmd输入dot -version出现下面这种就安装成功了

再运行代码就可以画图