What are Identifiers in Python?

A Python identifier is a name used to identify a variable, function, class, module or other object. An identifier starts with a letter A to Z or a to z or an underscore (_) followed by zero or more letters, underscores and digits (0 to 9).

Here are naming conventions for Python identifiers −

  • Class names start with an uppercase letter. All other identifiers start with a lowercase letter.
  • Starting an identifier with a single leading underscore indicates that the identifier is private.
  • Starting an identifier with two leading underscores indicates a strongly private identifier.
  • If the identifier also ends with two trailing underscores, the identifier is a language-defined special name.

Keywords cannot be used as identifiers. Example:

global = 1

Output

File "<interactive input>", line 1 global = 1 ^ SyntaxError: invalid syntax

We cannot use special symbols like !, @, #, $, % etc. in our identifier. Example:

a@ = 0

Output

File "<interactive input>", line 1 a@ = 0 ^ SyntaxError: invalid syntax