python programming

 

03. PROGRAMMING IN PYTHON

v Python: - Python is an object oriented programming language.

àIt is a very high level language.

àIt is an advanced version of JAVA programming language.

àIt is a case sensitive language i.e. code written in uppercase and lowercase both are treated as different.

àIt is a platform independent language which means programs

Written on one computer can run on another computer.

àThe file extension name of python is “.py”

àIt is a simplest language than another programming language like: C, C++, JAVA etc.

àIt is a portable or robust language which means that can support another computer.
It is an interpreted language and also compatible with all operating system.

àThere are various version of python has been released like python v0.1.0, python v3.5.1, v2.7.0, python v3.5.1 etc.

v How to install python?

1) First of all open web browser and type ‘PYTHON.ORG.’

2) There are various download links available.

3) Click on ‘download windows x 86-84’ web based installer.

4) Now, downloading file double click on installer file.

5) After that click on RUN button.

6) Click on ‘install now’ option.

7) And finally click on CLOSE button.

 

v To working with python we have to install “IDLE IDE”

àThe interactive interpreter of python is called “Python Cell”. It creates, debug, run, edits python program.

 

 

Note: - Python was developed by Gaido Van Rassum in 1980.

Full form of IDE is “Integrated development environment”.

 

 

àThere are two modes to work in python:-

1) Interactive mode: - In this mode we type the code in only one line at command prompt ‘>>>’.

 

àHere, python interpreter interpretes the command and gives output when we press “Enter” button.

E.g:- >>>10+20

30

 >>>

To work in interactive mode: -

1) First of all open the IDLE.

2) Type the command at python prompt.

3) After pressing ‘Enter’ button display the output.

E.g: - >>>10+20

30

>>> 

Note: -Python shell is a layout screen where we can type command.

To restart the python shell we have to press “Ctrl + F6”.

2) Script mode: - In this mode we type the command in more than one line; and after that save it with file name in python file.

àIt is very simple than interactive mode.

àCode of script mode can be used in future.

àTo display output we have to print ( ) function.

àTo execute this code we have to press F5.

 

To work in script mode: -

1) First of all open python shell.

2) Go to file option and select ‘new file’ option & click on it.

3) After that type the code in open window of python shell.

4) After that save the code in python folder.

5) Go to ‘run’ menu & select ‘Run module F5’ option & click on it.

E.g: - A=30

B=40

C=A+B

Print (C)

 

v Character Set: - It is a combination of alphabets, alphabets, digits and some special character ($, #, @, %).

 

v Tokens: - It is a smallest unit of a program.

 

There are five types of tokens: -

1) Identifiers.

2) Keywords.

3) Literals.

4) Punctuators.

5) Operators.

 

v Identifiers: - It is the fundamental unit of a program which is used to identify the elements of a program.

 

Rule for creating identifiers: -

1) Identifier name always started with either character or underscore (-) symbol.

2) Identifier name should not start with digits.

3) It should be not keywords.

E.g: - AB, -AB, A1 etc.

 

v Keywords: - It is reserved word which has a specific meaning or function.

àThere are 33 keywords in python.

false	return	else	lambda	yield	from	def
none	import	is	with	break	or	if
true	elif	while	assert	for	continue	raise
and	in	as	finally	not	global
del	try	except	nonlocal	class	pass

 

 

v Literals: - It is a data items that never can be changes their value during education of program.

àIt is also known as “constant”.

There are four types of literals in python: -

1) Integer literals: - 1, 2, 3, 4 etc.

2) Character literals: - A, B, C, D etc.

3) Floating literals: - 1.0, 2.3, 7.4, 8.9 etc.

4) String literals: - “MICA”, “VKMTG” etc.

                                

v Punctuators: - It is a symbol which is used in a programming language. It is used to separate the line or terminated the line and other word.

E.g: - [ ], ( ), #, @, “” etc.

 

v Operator: - It is symbols that comes between the operands and perform some specific task like: addition, subtraction etc.

àOperand is a value or variable on which calculation is performed.

àThere are following categorize of the operator such as: unary, arithmetic, bitwise, relational, logical, assignment operator etc.

àThere are 3 kinds of operator Unary, Binary & Ternary operator etc.

 

1) Unary operator: - This type of operator performs operation with one operand.

àThere are two types of unary operator:

        i.          Postfix: - A++, B++, C++, A--, B--, C--, etc.

     ii.          Prefix: - ++A, ++B, ++C, --A, --B, --C etc.

 

2) Binary operator: - This type of operator performs operation between two operands.

E.g: - +, -, /, %, =, *etc.

 

3) Ternary operator: - This type of operator performs operation between two or more operands.

àIt is used in conditional statement.

E.g: - if (4%7==0)? True: False.

 

v Arithmetic operator: - An operator that perform arithmetic operation like: addition, subtraction, multiplication, division etc. is called “arithmetic operator”.

E.g: - +, -, *, /, %, // (Floor division), ** (Exponent) etc. 

 

v Relational operator: - An operator that performs comparing between arithmetical and logical expression is called relational operator.

àIt is also known as “comparison operation”.

E.g: - >, <, ==, ===, >=, <= etc.

 

v Logical operator: - An operator that performs logical operation is known as logical operator.

àThere are three types of logical operator: -

1) Logical AND (&&).

2) Logical OR (||).

3) Logical NOT (!).

 

v Logical ‘and’ operator: - This operator is written a ‘AND’. It combines two expressions into one. The resulting expression evaluates to ‘True’ only if both the conditions satisfies to ‘True’.

Logical and operator

Expression1	Expression2	Expression3
False	False	False
False	True	False
True	False	False
True	True	True

 

v Logical ‘or’ operator: - This operator is written as ‘or’. It combines two expressions into one. The resulting expression evaluates ‘True’ when either of the conditions satisfies to ‘True’.

Logical ‘or’ operator

Expression1	Expression2	Expression3
False	False	False
False	True	True
True	False	True
True	True	True

 

 

 

 

 

 

 

v Logical ‘not’ operator: - This operator is written as ‘not’. It works with single expression or operand, i.e. it is a unary operator. This operator negates or reverses the truth value of the expression. In other words, if the expression is ‘True’, then the use of ‘not’ expression makes it ‘False and vice versa.

Expression	Not expression
False	True
True	False

Logical ‘not’ operator

 

                                                           

 

v Data type: - It shows the nature of variables and also defines what kind of data is to be stored in variables.

E.g: - int A here it show nature of A is “integer type”.

àThere are five standard of data type in python such as:

        i.            Numbers.

     ii.            String.

  iii.            List.

   iv.            Tuple.

      v.            Dictionary.

 

v Number data type: - This data type started with numeric value.

àIt is used for mathematical calculation.

Syntax: - variable name = value.

àThere are three types of number data type.

    i.            Integer.

 ii.            Float.

iii.            Complex.

 

v Integer: - It stores integer value.

E.g: - int A=10;

 

v Float: - It stores decimal value.

E.g: - Float A=4.7;

 

v Complex: - It stores complex number, like IB where A & B are: integer ‘I’ for imaginary number.

 

v String: - This data type store string value that is word within double or single quotes.

 

E.g: - String A= “MICA”.

v List: - It is a compound data type that contains items in the lists which is separated by commas (,) and enclosed within square brackets ([ ]).

Eg: - List A= [a, b, c, d];

 

v Tuple: - It is similar to list data type that contains items in the list which is separated by commas (,) and enclosed within parenthesis ( ).

Syntax: - Tuple name= (elements)

E.g: - Tuple A= (a, b, c, d);

 

v Dictionary: - This data type are kinds of key value pairs where key can be any number or string and values can be any arbitrary python object.

E.g: - A [‘Hello’] = “Welcome”.

              Key            Value

 

v General layout of python programs: -

# Documentation section, Declaration section, commands and expressions.

 

1) Documentation section: - This section consists of a set comment lines with the name of the program and other details.

àWe can also write the name of programmer and date.

àIt is not necessary to include in program.

àIn this line always proceeded with # tag.

2) Declaration section: - In this section value can be assigned to variables and literals.

àEqual sign is (=) used to assign the value.

E.g: - String A= “MICA”;

 

3) Commands: - In this section commands are written to make program and execute it.

àTo print this statement we should use “print command”.

E.g: - Print “Hello”;

 

4) Expressions: - An expression represents something which python evaluates and then produces result in the form of values.

E.g: - Sum= a+3;

 

v Print command: - This command is used to print the values.

 

v Input command: - This command/statement is used to getting some values from user after executing or running.

Syntax: - Variable name=data type (input (“message to be displayed”));