Month: December 2022

A closure is like a way to “remember” the values of variables from a function even after that function has finished running. Python lets us do this using nested functions.

Here’s a simpler explanation:

What Happens in a Closure?

1. You have a function inside another function.
2. The inner function uses variables from the outer function.
3. When the outer function finishes, the inner function “remembers” those variables because they’re part of its closure.

Example to Understand Closures

def greet(name):
    def say_hello():
        print(f"Hello, {name}!")  # 'name' is remembered here
    return say_hello

Here’s what happens step by step:

1. greet("Alice") is called.
2. Inside greet, the variable name is set to "Alice".
3. The say_hello function is returned but doesn’t run yet.
4. Later, when we call say_hello, it remembers that name is "Alice" and prints "Hello, Alice!".

Try it out:

hello_func = greet("Alice")  # Now we have the closure
hello_func()  # Outputs: Hello, Alice!

Even though greet has finished running, the say_hello function still remembers the value of name because of the closure.

Why Does This Work?

• Python stores the variables of the outer function in the closure of the inner function.
• These variables are preserved in memory even after the outer function is done.

You can check what the closure “remembers” like this:

print(hello_func.__closure__)  # Shows the variables saved in the closure

A Fun Analogy:

Think of the closure like a backpack that the inner function carries. It takes any variables it needs from the outer function and keeps them in the backpack so it can use them later, even if the outer function is long gone.

Let me know if this helps! 😊