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What can you do instead of a global variable?
In a scenario, where you need one central global point of access across the codebase, singletons are a good alternative for global variables. We can call a singleton as a lazily initialized global class which is useful when you have large objects — memory allocation can be deferred till when it’s actually needed.
What is a global state?
Consider the following definition of a global state: A global state is a set of local states which occur simultaneously. A different definition of a global state is possible based on the “causal domain” (a world based on the causally precedes relation).
Why is global mutable state bad?
If you say “state”, that is usually taken to mean “mutable state”. And global mutable state is totally evil, because it means that any part of the program can influence any other part (by changing the global state).
How to maintain immutability of a class with a mutable object?
Avoid methods which can change the mutable object. So in your example Employee class is immutable, because once it is created, you can’t change its state, because it has only getter methods. Address class is mutable because you can modify it with the setStreet method.
Why is the address class in Java mutable?
Address class is mutable because you can modify it with the setStreet method. So other class can modify this class. We can defend against this by taking a copy of the of the Address instance when it is passed in rather than trusting the reference to the instance we are given.
How to avoid using global variables in Python?
Here’s a list of some of the problems in these functions beyond modifying global state: using “yes” and “no” string literals instead of True / False boolean values. hardcoding values in functions, making them entirely single-purpose (they may as well be inlined).
How to save global variables in py file?
1: Start a new py file and copy all the variables and their starting values into the editor, like in the screenshot below, and save it as ‘globalstore.py’, or whatever name you want. The file needs to be saved in the same directory as your main py file is going to be run from.