Closure is an advanced feature in the Python language that can create a nested function inside a function, and the nested function can access the local variables of the outer function, even if the outer function has completed execution and returned. Simply put, a closure is a combination of a function and its associated reference environment.
To understand closures, you first need to understand some basic concepts.
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Function objects: In Python, functions can be treated as objects. Functions can be assigned to variables, passed as arguments to other functions, or as the return value of a function.
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Nested functions: In Python, you can define a function inside another function. Internal functions can access the variables of external functions, including parameters and local variables of external functions.
Now let's look at a simple closure example:
def outer_function(x):
def inner_function(y):
return x + y