Class and Namespaces 05

Namespaces in Python:
Namespace(s) is/are available at most Object Oriented languages, the clear idea of Namespaces is to declare names to variables and attributes. Let me share some sample to understand it clearly.

Error-Code 04

counter = 0

def counting_function():
    print("Start:: ",  counter)
    counter += 1
    print("After Counter::", counter)
    
    
if __name__ == "__main__":
    counting_function()

O/P

..
UnboundLocalError: local variable 'counter' referenced before assignment

Note: To address this NameSpace and scope of variable are applied.

"global" keyword prefix to counter variable. If you add global keyword out-side the NameSpace, will result to error, try and check it by self for understanding declaration errors.

Fixed Code 04

counter = 0

def counting_function():
    global counter
    print("Start:: ",  counter)
    counter = counter + 1
    print("After Counter::", counter) 

if __name__ == "__main__":
    counting_function()

O/P

..

Start::  0
After Counter:: 1 

Fixed Code 04.1

global counter

def counting_function():
    counter = + 1
    print("After Counter::", counter) 

O/P

..

After Counter:: 1

Note: From fixed code 04, if "counter = counter + 1" is ignored code works perfect, due to 

assignment . Lets look on one more example.

Error-Code 05

gl_variable = 5
def namespace_function():
    i_variable = 6
    print("Global variable:: ", gl_variable)
    print("NS variable:: ", i_variable)
    
    def inner_function():      
        i_value = 7
        print("Inner value::", i_value)
        print("NS variable scope::",i_variable)
        
if __name__ == "__main__":
    namespace_function()

    #inner_function() -- NameError: name 'inner_function' is not defined

O/P

.. 

Global variable::  5
NS variable::  6

Note: A new approach of Namespace(s) declare to maintain the scope of variables in this suite/block of code.

inner_function() is not called from main will result to an Error, so we have to call inner_function from scope of namespace_function fix code follows.

Fixed Code 05

gl_variable = 5
def namespace_function():
    i_variable = 6
    print("Global variable:: ", gl_variable)
    print("NS variable:: ", i_variable)
    
    def inner_function():      
        i_value = 7
        print("Inner value::", i_value)
        print("NS variable scope::",i_variable)
    
    inner_function()
        
if __name__ == "__main__":
    namespace_function()

O/P

..
Global variable::  5
NS variable::  6
Inner value:: 7
NS variable scope:: 6

Namespace for inner_function() call-scope, is with in the parent function itself.

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