库功能：
Python interface to the igraph high performance graph library, primarily aimed at complex network research and analysis.
>>> igraph.test.test()
测试安装成功
2.Graph plotting in igraph on Windows
http://hal.elte.hu/~nepusz/development/igraph/tutorial/install.html
先安装pycairo 然后还有几个相关的dll，
http://alex.matan.ca/2009/11/21/cairo-integration-with-wxpython-installation-of-python-wxpython-pycairo-and-cairo-2-d-graphics-library-on-windows-xp/
分别下载：libcairo-2.dll、libpng13.dll、zlib1.dll;然后复制到环境变量path中包含的路径中
3. launch Python again and check if it worked:
>>> from igraph import *
>>> g = Graph.Famous("petersen")
>>> plot(g)
