def f():
print(s)
s = "Perl"
print(s)
s = "Python"
f()
print(s)
If we execute the previous script, we get the error message:
UnboundLocalError: local variable 's' referenced before assignment
The variable s is ambigious in f(), i.e. in the first print in f() the global s could be used with the value "Python". After this we define a local variable s with the assignment
s = "Perl"