Game of Greed 2

Python Scope & the LEGB Rule:

Scopes overview

• Determines how variables and names are looked up, or their visibility in your device.
• The scope depends of the place where a variable is created.
• The scope is presented in LEGB rule (Local, Enclosing, Global, Built-in).
• A name will only be accessible in its scope.

Scope types

1. Global scopes: avalible for all code.
2. Local scopes: available only within the scope.

You can create Python names through one of the following operations: [^1] |Operation |Statement | | ———– | ———– | |Assignments | x = value | |Import operations |import module/from module import name | |Function definitions |def my_func()| |Argument definitions in the context of functions |def my_func(arg1, arg2,… argN)| |Class definitions | class MyClass|

Note: There’s an important difference between assignment operations and reference or access operations. When you reference a name, you’re just retrieving its content or value. When you assign a name, you’re either creating that name or modifying it.

Python Scope vs Namespace

• Python scopes are implemented as dictionaries that map names to objects(called namespaces).
• This is the mechanism of storing names. They’re stored in a special attribute called .dict.

Using the LEGB Rule for Python Scope

• Local scope –> is the code block or body of any Python function or lambda expression.
• Enclosing (or nonlocal) –> only exists for nested functions, The names in the enclosing scope are visible from the code of the inner and enclosing functions.
• Global (or module) –> contains all of the names that you define at the top level of a program or a module.
• Built-in scope –> This scope contains names such as keywords, functions, exceptions, and other attributes that are built into Python. names are available from everywhere in your code, aytomatically loaded whenever you run a script or a program.

The LEGB rule is a kind of name lookup procedure, which determines the order in which Python looks up names. For example, if you reference a given name, then Python will look that name up sequentially in the local, enclosing, global, and built-in scope. If the name exists, then you’ll get the first occurrence of it. Otherwise, you’ll get an error.

Differences between LEGB rules

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Big O notation

• How much time and space in memory it being consumed while an algorithm is being executed.
• It is a way to measure how the algorithm will process to increasing data in terms of time and space.
• A way of comparing different algorithm.
• Big O notation gives the worst case senario.
• Computational complexity:
  1. O(1) : constant running time.
  2. O(n) : linear running time.
  3. O(n^k): polynomial running time.
  4. O(log n): logathimic running time.
  5. O(n log n): log-linear running time.

More [^1]:https://realpython.com/python-scope-legb-rule/