title: Python Variables Names and Binding
Having objects isn’t useful unless there is a way to use them. In order to use an object, there must be a way to reference them. In Python this is done by binding objects to names. A detailed overview of can be found here
One way this is done is by using an assignment statement. This is commonly called assigning a variable in the context of Python. If speaking about programming in the context of other languages, binding an object to a name may be more precise.
>>> some_number = 1 >>> print(some_number) 1
In the example above, the target of the assignment statement is a name (identifier),
some_number. The object being assigned is the number 1. The statement binds the object to the name. The second statement, we use this binding
some_number refers to.
The identifier is not preceeded by a type. That is because Python is dynamically-typed language. The identifier is bound to an object that does have a type, however, the identifier itself can be rebound to another object of a different type:
>>> some_variable = 1 >>> print(some_variable) 1 >>> some_variable = "Hello campers!" >>> print(some_variable) Hello campers!
When naming variables, you must follow these rules:
- A variable name must start with a letter or the underscore character
- A variable name cannot start with a number or special characters ([email protected]#%^&*, etc.)
- A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
- Variable names are case-sensitive (num, NUM and Num are three different variables)