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    IDENTIFIERS
                     An identifier is a sequence of characters taken from the Python character set. It refers to variables,
                     functions and arrays. The rules for identifiers are:

                       Only letters, digits and an underscore are permitted.
                       Must start with a letter between A to Z or between a to z or an underscore (_).
                       Uppercase and lowercase are distinct because Python is a case sensitive language.

                       Special characters are not allowed.
                     Some examples of valid identifiers are Myvar, myvar_1, Sum_of_the_numbers, PASS and _Sum.
                     Some examples of invalid identifiers are False, Var^2, Var 1 and 1var.

                     KEYWORDS

                     Keywords are the reserved words. They are predefined words. Keywords cannot be used as an
                     identifier.
                     Some commonly used keywords in Python are given below:

                      False       assert         del            for           in               or             while
                      None        break          elif           from          is               pass           with
                      True        class          else           global        lambda           raise          yield
                      and         continue       except         if            nonlocal         return         async

                      as          def            finally        import        not              try            await

                     CONSTANTS OR LITERALS

                     Constants are fixed values that do not change during the execution of a program. Literals are the
                     type of constant. Literals refer to any number, text and other information that represents a value.
                     Python supports the following literals:

                                                  Literals                     Example

                                           String literals           “hello”, ‘12345’
                                           Integer literals          0, 1, 2, -1, -2

                                           Long literals             89675

                                           Floating-point literals   3.14
                                           Complex literals          12j

                                           Boolean literals          True or False
                                           Special literals          None

                                           Unicode literals          u“hello”
                                           List literals             [5,6,7]

                                                                                        Tokens and Data Types in Python  97

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