var=1
class ClassName():
    def __init__(self):
       # ...
    #some other methods that do not need global variable here

    def Met():
        #do some other stuff that needs the global var

""" Approach one """
var=1
class ClassName():
    def __init__(self):
       # ...
    #some other methods that do not need global variable here
    def Met():
        # needs the global var to operate
        global var
        # do some stuff with var (including editing)


""" Approach two"""
var=1
class ClassName(var):
    def __init__(self):
       # ...
    #some methods that do not need global variable here
    def Met(var):
        # do some stuff with var (including editing)

var=1
def func1():
    #do some stuff
    #do not need global variable here

    def func2():
        #do some other stuff
        # need the global var

    func2() # call func2

var=1
def func1():
    def func2():
        global var
        var = 2       # global variable updated
    func2()
func1()
print(var)

var=1
def func1(var):
    def func2(var):
        var = 2
        print(var)    # local var is printed, global var unchanged
    func2(var)
func1(var)
print(var)           # global var is printed