Names and Scopes in Python

Since Python is a dynamically-typed language, variables in Python come into existence when you first assign them a value. On the other hand, functions and classes are available after you define them using def or class, respectively. Finally, modules exist after you import them.

globals()

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Python globals() function is a built-in function used to update and return a dictionary of the current global symbol table. The functions and variables that are not associated with any class or function are stored globally. It is mostly used for debugging purposes to see what objects the global scope actually contains

nonlocal

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The nonlocal keyword is used to work with variables inside nested functions, where the variable should not belong to the inner function. Use the keyword nonlocal to declare that the variable is not local

Unlike global, you can’t use nonlocal outside of a nested or enclosed function. To be more precise, you can’t use a nonlocal statement in either the global scope or in a local scope.

Big O notation

Big O notation is a mathematical notation that describes the limiting behavior of a function when the argument tends towards a particular value or infinity. … In computer science, big O notation is used to classify algorithms according to how their run time or space requirements grow as the input size grows