Python Identifiers

An identifier is a name given to entities like class, functions, variables, etc. It helps to differentiate one entity from another.

Rules for writing identifiers

• Identifiers can be a combination of letters in lowercase (a to z) or uppercase (A to Z) or digits (0 to 9) or an underscore _. Names like myClass, var_1 and print_this_to_screen, all are valid example. 
• An identifier cannot start with a digit. 1variable is invalid, but variable1 is perfectly fine. 
• Keywords cannot be used as identifiers

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

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

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

• Identifier can be of any length.

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