Python user defined Data Types

The data types which are created by the programmers are called 'user-defined' data types. For example, an array, a class, or a module is user-defined data types. We will discuss about these data types later.


  1. An identifier is a name that is given to a variable or function or class etc.
  2. Identifiers can include letters, numbers, and the underscore character (_).
  3. They should always start with a nonnumeric character.
  4. Special symbols such as ?, #, $,%, @ etc are not allowed in identifiers.
  5. Some examples for identifiers are salary, name11, gross_income, etc.

We should also remember that Python is a case sensitive programming language. It means capital letters and small letters are identified separately by Python.

For example, the names 'num' and 'Num' are treated as different names and hence represent different variables.