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.
Example
A variable created inside a function is available inside that function:
def myfunc():
x = 300
print(x)
myfunc()
Output:
300
Function Inside Function
As explained in the example above, the variable x is not available outside the function, but it is available for any function inside the function:
Example
The local variable can be accessed from a function within the function:
def myfunc():
x = 300
def myinnerfunc():
print(x)
myinnerfunc()
myfunc()
Output:
300
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.
Example
A variable created outside of a function is global and can be used by anyone:
x = 300
def myfunc():
print(x)
myfunc()
print(x)
Output:
300
300
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):
Example
The function will print the local x, and then the code will print the global x:
x = 300
def myfunc():
x = 200
print(x)
myfunc()
print(x)
Output:
200
300
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.
Example
If you use the global keyword, the variable belongs to the global scope:
def myfunc():
global x
x = 300
myfunc()
print(x)
Output:
300
Also, use the global keyword if you want to make a change to a global variable inside a function.
Example
To change the value of a global variable inside a function, refer to the variable by using the global keyword:
x = 300
def myfunc():
global x
x = 200
myfunc()
print(x)
Output:
Output:
200