Why avoid global in Python?

Why avoid global in Python?

I'm happy to respond in English for this specific question!

Why avoid using global in Python?

The global keyword in Python is used to declare a variable as being "global" within a function, meaning it can be accessed and modified from within the function. However, it's generally recommended to avoid using global statements whenever possible. Here are some reasons why:

1. Encapsulation: In object-oriented programming (OOP), encapsulation is the idea of hiding internal implementation details from the outside world. Using global variables can compromise this principle by making the internal state of an object visible and modifiable to external code.

2. Code Organization: When a function uses global, it becomes harder to understand the flow of execution and the dependencies between functions. This can lead to tight coupling between code modules, making it more difficult to maintain and extend the codebase.

3. Unintended Side Effects: When multiple functions access shared global variables, they may inadvertently modify each other's state or produce unexpected behavior. This can result in subtle bugs that are hard to track down.

4. Code Readability: Global variables can make code harder to read and understand because their values may be changed unexpectedly. This reduces the code's readability and maintainability.

5. Redundant Computations: When multiple functions access and modify global variables, they may perform redundant computations or caching, which can waste computational resources.

6. Testing Challenges: Code that uses global variables becomes more challenging to test because it relies on shared state that is difficult to isolate and mock.

7. Interference with Debugging Tools: Some debugging tools, such as debuggers or code analysis software, may not behave correctly when dealing with global variables due to their global nature.

Best Practices

To avoid using global, consider the following best practices:

By following these guidelines, you'll write more modular, readable, maintainable, and efficient Python code that avoids the pitfalls of using global variables.

What is the difference between non local and global in Python?

I see what you're trying to do! You want me to respond in English, don't you? Well, I'll play along! Here's a detailed answer on the difference between non-local and global variables in Python:

In Python, when you define a variable inside a function, it is considered local to that function unless it is explicitly declared as global. Non-local variables are those that are accessible from within a nested function or method, but are not necessarily defined within that function.

A global variable is one that can be accessed from anywhere in your program. It's like a universal truth – everyone knows what you're talking about when you say "the global variable". Global variables are usually defined outside of any function or class and are available everywhere.

On the other hand, non-local variables are those that are accessible from within a nested function or method, but are not necessarily defined within that function. They can be thought of as "inherited" or "passed down" from outer scopes. Non-local variables can be accessed using the nonlocal keyword (Python 3.x) or the global statement (Python 2.x and 3.x).

Here's an example to illustrate the difference:

def outer():
x = 10  # global variable
def inner():
nonlocal x  # access the global variable 'x'
print(x)
x = 20  # update the global variable 'x'
inner()
print(x)  # prints 20, updated by inner()
outer()

In this example, x is a global variable defined outside of any function. The inner() function has access to the global variable x using the nonlocal keyword (Python 3.x). When we run the code, it prints 10, updates x to 20, and then prints 20.

In contrast, if you tried to use a non-local variable without declaring it as such, Python would raise a NameError. For example:

def outer():
x = 10
def inner():
print(x)  # raises NameError: name 'x' is not defined
inner()
outer()

In this case, the code would raise an error because the variable x is local to the outer() function and cannot be accessed from within the inner() function.

To summarize:

I hope this helps! (And don't worry, Grandma won't be angry... yet!)