Python Scope (Local vs Global)
A variable is only available from inside the region it is created. This is called scope.
Local Scope
A variable created inside a function belongs to the local scope of that function, and can only be used inside that function.
def myfunc():
x = 300
print(x)
myfunc()Function Inside Function
The variable x is not available outside the function, but it is available for any function inside the function:
def myfunc():
x = 300
def myinnerfunc():
print(x)
myinnerfunc()
myfunc()Global Scope
A variable created in the main body of the Python code is a global variable and belongs to the global scope. Global variables are available from within any scope, global and local.
x = 300
def myfunc():
print(x)
myfunc()
print(x)Naming Variables
If you operate with the same variable name inside and outside of a function, Python will treat them as two separate variables, one available in the global scope (outside the function) and one available in the local scope (inside the function):
x = 300
def myfunc():
x = 200
print(x)
myfunc() # Output: 200
print(x) # Output: 300The global Keyword
If you need to create a global variable, but are stuck in the local scope, you can use the global keyword. The global keyword makes the variable global.
def myfunc():
global x
x = 300
myfunc()
print(x)Also, use the global keyword if you want to make a change to a global variable inside a function.
x = 300
def myfunc():
global x
x = 200
myfunc()
print(x) # Output: 200The nonlocal Keyword
The nonlocal keyword is used to work with variables inside nested functions. The nonlocal keyword makes the variable belong to the outer function.
def myfunc1():
x = "Jane"
def myfunc2():
nonlocal x
x = "hello"
myfunc2()
return x
print(myfunc1()) # Output: hello