What is local vs global in Python?

What is local vs global in Python?

A fundamental concept in Python programming!

Local Variables:

In Python, a local variable is a variable that is defined within a specific scope or block of code. This scope can be a function, a loop, or an if statement. Local variables are only accessible within the scope where they are defined and are discarded when the scope exits.

For example:

def my_function():
x = 10  # local variable x
print(x)  # Error: x is not defined outside the function
my_function()

In this example, x is a local variable defined within the my_function scope. It can only be accessed within that scope and is discarded when the function exits.

Global Variables:

On the other hand, global variables are defined outside any specific scope or block of code. They have access to all parts of your Python program and retain their values even after the execution of a function.

Here's an example:

x = 20  # global variable x
def my_function():
print(x)  # prints 20, accessing global variable x
my_function()
print(x)  # still prints 20, as it is a global variable

In this example, x is a global variable defined outside any function. It can be accessed and modified from within any part of your program.

Key differences:

Best practices:

When working with variables in Python, it's essential to understand when to use local and global variables. Here are some best practices:

Conclusion:

In Python, understanding the difference between local and global variables is crucial for writing clean, efficient, and maintainable code. By applying best practices, you'll avoid common pitfalls and make your code easier to read, debug, and modify.

What is a local scope in Python?

I'm happy to respond in English!

A local scope in Python refers to the memory space where variables and functions are stored within a specific block of code, such as a function or a loop. In other words, it's the area where names (like variables) are looked up when they're used.

When you define a variable inside a function, that variable is said to be in scope for that function only. This means that if you call another function from within this original function, the variables defined in the original function are not automatically passed to or accessible by the new function. Similarly, any changes made to those variables within the original function do not affect their values outside of that function.

Here's a simple example:

def outer():
x = 10  # x is local to outer()
def inner():
nonlocal x  # 'nonlocal' is used to modify x in outer()
print(x)  # prints 10, because x is looked up in the local scope of outer()
x += 1
inner()
print(x)  # still prints 11, because changes made within inner() affect x in outer()
outer()
print(x)  # raises a NameError, because x is no longer in scope

In this example, x is initially defined inside the outer() function. Within that function, we define another function, inner(), which also modifies x. Because we used the nonlocal keyword to indicate that we want to modify an outer (i.e., non-local) variable, we can still access and change x within inner(). When we print x again after calling inner(), we see that it has indeed been incremented.

Now, if we were to call another function from within outer() that didn't use the nonlocal keyword or wasn't declared as a nested function, it would not have access to variables like x. That's because those variables are only in scope for the specific block of code where they were defined.

To illustrate this further, consider what happens when we try to access x directly within inner() without using nonlocal:

def outer():
x = 10
def inner():
print(x)  # raises a NameError, because x is not in scope for inner()
inner()
outer()

In this case, Python raises a NameError when trying to access x, because inner() doesn't know about the outer x.

So, to summarize: local scopes are where variables and functions are stored within a specific block of code (like a function or loop), and they're not automatically accessible outside that scope. You can use the nonlocal keyword to modify variables from an outer scope, but without it, those variables remain isolated within their respective scopes.

Hope this explanation helps!