Literals
A literal is a directly defined value. "25" is a literal. So is true
In Python, this is an example of a literal:
print(5 + 3) Both 5 and 3 are literals in this context, because they are definied exactly where they are used.
Variables
A variable is an object with an assigned value that can be referenced elsewhere in the program. It is useful for dynamically updating a value.
bobAge = 50 is a variable.
Naming conventions should be followed when naming variables to prevent misunderstandings.
If your variable is called penisland there may be issues with people not reading Pen Island.
So naming a variable pen_island would be better. This is what PEP8 recommends, and is therefore the best option for naming variables in Python (if you want people to like you).
Conventional naming would be penIsland though. Camelcase means the first word of a variable is lowercase and then all additional words in the name should start with a capital.
Note
Variable names can also be called an identifier.
Constants
A constant is a variable that CANNOT be changed after definition. The idea of a constant is to define a reused value once at one point in the code, and then allow for it to be used everywhere. if you want to change the speed of the player in your game, you can change the constant at first definition, avoiding a huge amount of refactoring.
Python does not support constants natively
Instead, use a fully capitalised variable name and do not change it. This method is flawed, but it’s the best one avaliable.
SPEED = 5.0
The next page is subroutines