What are globals vs locals in Python?

What are globals vs locals in Python?

I'd be happy to explain the concept of globals and locals in Python.

In Python, variables can be classified into two categories: global variables and local variables. The main difference between these two types of variables is their scope, which determines where they are accessible from within a program.

Global Variables

A global variable is one that is defined outside any function or block of code. In other words, it is a variable that is defined at the top level of a Python module. Global variables can be accessed and modified anywhere in the program, as long as the code has access to the global scope.

Here's an example:

x = 10  # this is a global variable
def foo():
print(x)  # prints 10
foo()
print(x)  # prints 10

In this example, x is defined at the top level of the module, so it is a global variable. The function foo() can access and print the value of x, as can any other code that has access to the global scope.

Local Variables

A local variable, on the other hand, is one that is defined within a specific block of code, such as a function or a loop. Local variables are scoped to the block in which they are defined and are not accessible outside of that block.

Here's an example:

def foo():
x = 10  # this is a local variable
print(x)  # prints 10
foo()
print(x)  # raises a NameError

In this example, x is defined within the function foo(), so it is a local variable. The value of x is only accessible within that function and cannot be accessed from outside the function.

Why Care About Scoping?

You may wonder why you need to care about scoping in Python. After all, isn't it just easier to define all your variables at the top level of your program?

The answer is no! While it might seem convenient to define all your variables as global, there are several good reasons why you should avoid doing so:

By using local variables whenever possible, you can avoid these problems and write more robust, maintainable code.

Conclusion

In conclusion, Python has two types of variables: global variables and local variables. Global variables are defined at the top level of a module and can be accessed anywhere in the program. Local variables, on the other hand, are scoped to a specific block of code and cannot be accessed outside that block. Understanding the difference between these two types of variables is crucial for writing good Python code, as it helps you avoid namespace pollution, conflicting variable names, and security issues.

What is a nonlocal in python w3schools

I'm happy to help! However, since you asked me to respond only in English, I'll do my best to provide an accurate and detailed explanation of what a Non-Local Statement (Nonlocal) is in Python, as per W3Schools.

What is a Non-Local Statement in Python?

In Python, non-local statements are used to modify or reassign variables that are defined outside the current scope. A non-local statement allows you to access and modify variables from an outer scope (i.e., a scope that is not directly enclosed by the inner scope). This can be achieved using the nonlocal keyword.

How do Non-Local Statements work?

When you use the nonlocal keyword in a function, it declares that a variable is non-local. In other words, it's telling Python that this variable is defined outside the current function scope. Here's an example:

x = 10
def outer():
x = 20
def inner():
nonlocal x
print("Inner: ", x)
x = 30
print("Inner: ", x)
inner()
print("Outer: ", x)
outer()
print("Global: ", x)

In this example, the nonlocal statement inside the inner() function tells Python that it's working with the variable x, which is defined in the outer scope (i.e., outer()). When you run this code, the output will be:

Inner: 20
Inner: 30
Outer: 30
Global: 10

As you can see, the value of x inside the inner function changes to 30. This is because the non-local statement allows us to access and modify the variable x, which was defined outside the current scope.

Key Takeaways

I hope this helps!