def AppenedFuncShortHandOperator(addList):
    addList+=[4]
	
def AppenedFuncRegularAssignment(addList):
    addList= addList + [4]
    
mylist=[1,2,3]
AppenedFuncRegularAssignment(mylist)
print(mylist) # expected=[1,2,3,4], actual= [1,2,3]
AppenedFuncShortHandOperator(mylist)
print(mylist) # expected=[1,2,3,4], actual= [1,2,3,4]