Why glGenVertexArray()gives access violation error?

[Mekire]

I haven't touched this or openGL in ages so you are out of luck on details, but I successfully used this function here:
https://github.com/Mekire/gltut-pygame/b...anually.py

are there difference between 'vao=glGenVertexArray(1)' and glGenVertexArray(1,vao)

The second one looks like it is from the C version as you presumably pass it a struct pointer to populate.  The first version is the one you should be using.