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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]




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