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

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!)

What does nonlocal mean in Python?

I'd be happy to explain what "nonlocal" means in the context of Python!

In Python, a nonlocal statement is used to modify a variable that is not local and not global either, but is defined in an outer ( enclosing) scope. In other words, it allows you to change the value of a variable in a parent function or class from a nested function.

To better understand this concept, let's take a look at an example:

def outer_func():
x = 10
def inner_func():
nonlocal x
x = 20
print(x)  # Output: 20
inner_func()
print(x)   # Output: 20
outer_func()
print(x)      # Error! 'x' is not defined.

In this example, inner_func has access to the variable x declared in outer_func. When we modify x inside inner_func, it persists even after the function call finishes. If we were only modifying a local variable, its value would be lost when the function returns.

The nonlocal statement is used to indicate that you want to modify the variable x from an outer scope. Without nonlocal, Python wouldn't know which variable x you're referring to, since there are multiple scopes (global and local) with variables named x.

Here's another example:

class Parent:
x = 10
class Child(Parent):
def init(self):
self.x = 20
def modify_x(self):
nonlocal x
x = 30
child = Child()
print(child.x)   # Output: 20
child.modify_x()
print(child.x)   # Output: 30

In this case, we have a class hierarchy where Child inherits from Parent. The variable x is defined in Parent, but we're trying to modify it in the modify_x method of Child. If we didn't use nonlocal, Python would create a local variable x in the modify_x method, which wouldn't affect the original x in Parent.

In summary, nonlocal is used to access and modify variables defined in an outer scope from within a nested function or class. This allows you to maintain state across different scopes and functions, making your code more flexible and reusable.

I hope this explanation helps clarify what "nonlocal" means in the context of Python!