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Mastering Python: Closures and Decorators

What are scopes?What are scopes?

The scope is an environment that stores variables, functions, and other objects in a program.

Let's consider the example:

Code Description
In this Python code, there are two different scopes for the variable number:

  1. Global Scope:
    2. The variable number is defined outside of any function, at the top level of the code. This makes it a global variable. The global scope allows this variable to be accessible from anywhere within the code, including inside functions.

    The first print statement accesses the global variable number and prints its value, which is 15.

  2. Local Scope (Function Scope):
    3. Inside the function some_function(), a new variable number is defined. This variable has a local scope, meaning it is only accessible within the function and does not affect the value of the global number variable.

    The print statement inside some_function() accesses the local variable number and prints its value, which is 256.

After calling the function some_function(), the global number variable remains unchanged.

The number variable in the regular code and the number in the some_function have the same name but are different variables because they are placed in different scopes.

Scope Types

  • Built-in
  • Global
  • Non-local (Enclosing)
  • Local

Built-in Scope

This is a scope of Python built-in tools. For example, the built-in len() function. You can use this function everywhere in your code.

Global Scope

It's the main scope of your code. This scope contains the variables, functions, and other objects you define.

Non-local (Enclosing) Scope

The non-local scopes are scopes between global and local scopes. The non-local scope can be enclosed and transformed into the enclosing scope. It will be described in the next section.

Local Scope

This scope is used for functions. Every function has a unique scope that deletes after the function executes.

How do scopes work?

Let's take a look at an example and analyze it.:

Code Description
Inside the function add(), a variable result is defined. This variable has a local scope, meaning it is only accessible within the function and does not exist outside of it.

When attempting to print the result variable outside the add() function, a NameError is raised. This is because result is a local variable, and it doesn't exist in the global scope.

Here the global scope has the variables number and string and the add() function.
The len() and print() functions are used from the built-in scope.
The add() function has a local scope with the variables first, second, and result. Arguments are variables defined inside the function, and the received data assign to these variables.

Everything was clear?

Section 1. Chapter 1