Identifiers

In Python, keywords are predefined and reserved words with specific meanings. The syntax of the code is defined by keywords. The keyword can't be used as a variable name, function name, or identifier. Except for True and False, all keywords in Python are written in lower case. Let's have a look at each of the 33 keywords in Python 3.7 one by one.

Identifiers: An identifiers in python is a name that is used to identify a variable, function, class, module, or other type of object. The identifier is made up of a series of digits and underscores. The identification should begin with a letter or an Underscore and then be followed by a digit. A-Z or a-z, an UnderScore (_), and a digit are the characters (0-9). Special characters (#, @, $, percent,!) should not be used in identifiers.

Rules for writing identifiers

1. 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.
2. An identifier cannot start with a digit. 1variable is invalid, but variable1 is a valid name.
3. Keywords cannot be used as identifiers.

   global = 1

   Output

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

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

   a@ = 0

   
   Output

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

5. An identifier can be of any length.