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3.2 Tokens

        The word lexical refers to the vocabulary of a language. A statement in Python is a sequence of its lexical components,
        called tokens, such as numbers, parentheses, and commas. Python has the following tokens (to be discussed in this
        section): keywords, identifiers, literals, delimiters, and operators (see Fig 3.1).

                                                        Keywords




                                        Operators                       Identifiers
                                                         Python
                                                         Tokens


                                       Delimeters                       Literals

                                                  Fig 3.1: Tokens in Python

        3.2.1 Keywords

        Keywords (also called reserved words) are words whose meaning and usage are predefined in a programming language.
        Thus, a keyword cannot be used for any purpose other than the one defined by the language. Every programming
        language has a set of keywords. Some of the most commonly used keywords are shown in Table 3.2. Note that the
        keywords are case-sensitive. For example, while True is a keyword, true is not.

                                                Table 3.2: Keywords in Python
                                     True       False         class        is
                                     finally    continue      for          while

                                     None       try           except       def
                                     not        and           or           if
                                     elif       assert        else         import
                                     pass       break         raise        global
                                     in         from          with         print
                                     input      return        continue     as

        To display the keyword list of Python, we can use the keyword module in Python.
         >>> import keyword
         >>> keyword.kwlist
                ['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await', 'break', 'class',
              'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global',
              'if',  'import',  'in',  'is',  'lambda',  'nonlocal',  'not',  'or',  'pass',  'raise',
              'return', 'try', 'while', 'with', 'yield']
        3.2.2 Identifiers
        An identifier is a name for a Python object. For example, the identifiers name, age, rollNo, and marks may
        be used to refer to the name, age, roll number, and marks of a student. Like any other programming language, Python
        follows certain rules for framing identifiers, which are as follows:
          An identifier should begin with an uppercase or lowercase alphabet or an underscore (_).

           The first letter of the identifier (including an underscore) may be followed by an arbitrary combination of alphabets
          (a-z, A-Z), digits (0-9), and underscore (_).





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