PYTHON FOR CBSE CLASS 11 PART 2

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PYTHON FUNDAMENTALS

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PYTHON FOR CBSE CLASS 11

Character Set is a valid set of characters that a language recognizes. It could be any letter, digit or any symbol. Python has the following character set:

Letters	A – Z, a – z
Digits	0 – 9
Special Symbols	Space + – * / % // ( ) [ ] { } \  # , ;  :: ‘ ‘ “ “ @ _ < > = & ** != ==
Whitespaces	Blank Space, tabs, carriage return (enter sign), newline, formfeed
Other characters	Python can process all ASCII and UNICODE characters.

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TOKENS

The smallest individual unit in a program is called as Token or a lexical unit.

Python for cbse class 11 has following tokens:

Keywords                    Identifiers                    Literals                        Operators                    Punctuators

Keywords:       A keyword is a word having special meaning reserved by programming language.

Eg:-     False, True, print, id, and, or, not

Identifiers:      Identifiers are the names build by programmer and are used in program but are not keywords. Python has some rules to form an identifier –

            — An identifier is a long sequence of letters and digits with unlimited length.

            — The first character could be a letter or an underscore ( _ ).

            — Upper case and lower case is differently processed i.e. A is not process as a.

               Python is case sensitive language.

            — The digit 0 to 9 could be a part of identifier but cannot be the first character.

            — Identifier cannot contain any special character.

Eg:-     Valid Identifiers: Name                      _DT                 Z12345            My_File

            Invalid Identifiers:      29Abc My.File            False                dat$comp

Literals / Values:        Literals are also called constant values are data items have fixed values.

Python allows following literals.

          — String Literals:        These are created by enclosing text in single quotes or double quotes.

Eg: “ Hello World “   ,   ‘ My name is Sara ‘

                — Numeric Literals:    These could be integer types, floating types or complex types.

Integer literal:  These are whole numbers without any fractional part. These could be positive ( + ) or negative ( – ). Eg: 125, -78, +86

Floating literal: These have fractional part and could be represented in Fractional form or    Exponent form. Eg: 13.8, 2.0, -63.556  (fractional)

         1.7E, 0.58E02 (exponent form)

                        — Boolean literal: This could be either 0 or 1. 1 means True and 0 means False.

                        — Special Literal None: The None literal indicates the absence of value. It is also used to

                                                                indicate the end of the lists in Python.

            Operators:       These are used to perform operations on values and variables. They trigger some   

                                    computation.  

                        — Unary Operators: They only need one operand to operate upon.

                                                +          Unary Plus                  (Eg: +63,  951)

•       Unary Minus               (Eg:   -25,  -3.65)

~          Bitwise Complement (Eg:  8 bits-   complement(0) is 11111111  )

not       Logical negation         (Eg:   if x = 1,  not x = 0 )

                        — Binary Operators:    They need two operand to operate upon.

                                      Arithmetic Operators              ( + – * / // % ** )

                                      Identity operators                   ( is       is not )

                                      Relational Operators               ( <  >  <=  >=  ==  != )

                                      Assignment Operators             =  /=  +=  -=  %=  //=  **=  *=

                                                Logical Operators                   and                  or

                                                Membership Operators            in                     not in

            Punctuators:    Theses are symbols that are used in programming languages to organize structures,

                                    statements, expressions.

                                    Eg:       ‘ “ # \ ( ) { } [ ] @ : , =