Good day.

My query is about hoppings.

In fact, sometimes we have to change the onsite parameters when for instance a magnetic field is applied.

What is the difference between   hop[0].tag   and hop[1].tag

My second question 

the onsite fuction for example: def onsite(site, V):return V

why it depends on site where the shape functions for example 

def circle(pos): rsq = pos[0] ** 2 + pos[1] ** 2

depends on pos

Best

A BELAYADI