UNIT 1 PY .ppt - PYTHON PROGRAMMING BASICS

Programming Languages – Python History – Getting Started with Python – Writing a Simple program – Reading input from console – Identifiers – Variables, Assignment Statements and Expressions – Simultaneous Assignments – Named Constants – Data Types and Operators – Evaluating expressions – Augmented Assignment operators – Type conversion – Common Python Functions – Strings and Characters – Objects and Methods – Formatting Numbers and Strings.

 Computer programming languages are used to communicate through instructions in to a computer.  They are based on syntactic and semantic rule.  The computer can perform arithmetic operations, Using some specialized languages called the programming languages. Types:  Machine language or Low level language  Assembly language  High level language

Machine language: It is a machine language here the instruction written in binary code The machine language consists of 0’s and 1’s. It looks like: 10101000111 combination 0 & 1 are called as binary Here all the operation performed by using binary form. Example : C , C++.

programs written in machine level language are very difficult to read and modify. Assembly languages uses short descriptive word, known as mnemonic, to represent the each instructions. Example : add - adding numbers sub - subtracting numbers add 2, 4, result

Assembly source file ex: add 2, 3, result Machine code file 0101101010 assembler

programs are written by using high level language It consist of normal English and easy to learn and use. This program run in different types of machine. The instruction in high level programming language are called statement. Example: C, C++, Java, Python.

Programming languages divided into following category: Interpreted programming language Here most of the instruction executed directly, without compiling the program. Example: basic , python , pascal. Functional programming language It is defined as every calculation performed using mathematical evaluation(predefined function), Example : clean , curry. Compiled programming language Here compiler translate source code into machine code . Ex: c , c++ , java , visual basic.

Markup programming languages It is a artificial language it refer how the content will be displayed in webpage. Example: HTML , XML. Object oriented programming languages it is based on the concept of object, which may contain data , or attributes , methods .. Example: c++ , python…

It was created by Guido Van Rossum , python is derived from many other language including ABC , Modula 3, C , C++ , Algol-68 , Small talk , Unix. It got name from “Monty Python Flying Circus”. ‘python’ is a general purpose interpreted , interactive , object oriented ,and high level language, Released in 1991, it support both 32 and 64 bit integers and word size.

Python is High level language: It is look like a normal English. It is most compatible with human language. Python is interpreted: Python is processed at run time by the interpreter, you do not need to compile your program before executing it. Python support Object –Oriented, Python is a beginners language. Python is interactive : you can type into python prompt and interact with the interpreter directly to write the program.

 python ’ is general purpose ,structured programming language.  Easy to learn.  Easy to maintain.  Free and open source.  High level language.  Extensive libraries.

The python interpreter is a program that reads and execute python code , python programs stored in a file with an extension of .py To start the python interpreter by clicking python icon, or by typing python(idle) on a command line, then click file and new file. K.ANGURAJU , AP/CSE

An interpreter processes the program line by line , alternatively read the lines and perform computation. python Analyze and Executes program statements at the same time , K.ANGURAJU , AP/CSE

Interactive mode In this , to type the program into interactive mode , press enter then the interpreter displays the result. Here also The chevron (>>>) is a prompt that indicates that the interpreter is ready to enter the code. The interpreter provides an interactive environment to play with the language Here the results of expressions are printed on the same screen K.ANGURAJU , AP/CSE

K.ANGURAJU , AP/CSE Source code Input data Interpreter Output

writing a program that involves designing the algorithm then convert into programming code. Multiplication of two numbers A=10 B=20 C=A*B Print(c) Ex:2 Print(“enter into python world”)

Radius=5 Area=3.14*Radius*Radius Print(“area of circle is”, Area)

using input() function to ask the user input at run time. Syntax: Variable= eval(input(“statement”)) Description: Variable – dummy variable name eval() - convert the string into value Input() - reading input from user

A=eval(input(“Enter a value”)) B=eval(input(“Enter b value”)) C=A/B Print(“the result is”, c) Output: Enter a value 100 Enter b value 10 The result is 10

The character set are used to represent information. Also the characters used to write ‘python’ program , It is basically two types. 1. Source character set 2. Execution character set python character set Alphabets a… z A…..Z Execution character set Source character set White spaces Special characters Digits 0… 9 Escape sequence K.ANGURAJU , AP/CSE

 a - bell alert - beep sound  t - ,horizontal tab  n - new line  v - vertical tab K.ANGURAJU , AP/CSE

Identifiers are names given to the different program elements, Example: - variables , functions , list…etc Rules for naming identifiers: 1. It consist of letters and digits. 2. First character must be letter, or begin with _ 3. _ underscore also consider as character. 4. Both upper/lower character accepted. 5. No special character allowed. 6. identifier cannot be keyword. K.ANGURAJU , AP/CSE

Definition: A variable is an identifier, A variable is nothing but a reserved memory location (or) place holder to store values. Rules for naming variables: 1. It consist of letters and digits. 2. First character must be letter, or begin with _ 3. _ underscore also consider as character. 4. Both upper/lower character accepted. 5. No special character allowed. 6. Variables cannot be keyword K.ANGURAJU , AP/CSE

Variable declaration: syntax: v1,v2,v3…….etc Example: >>> a , b Initializing variables:(assignment statement) Initialization of variable can be done using assignment operator (=) ,variable can be initialized while declaration itself Syntax: variable name =value Example: >>> radius=10 >>> cutoff=198.4 >>> c=‘a’ K.ANGURAJU , AP/CSE

Local variables: A variable which is declared inside a function is called as local variable. Global variables/external variables: A variable which is declared outside a function is called as global variable. K.ANGURAJU , AP/CSE

Expression Expression is defined as combination of variables or constants are interconnected with operators. Syntax: variable=expression; There are following expression are: 1.Arithmetic expression It perform only arithmetic operation(+,-,/,%) Example: Num1=10 num2 = 20 sum=Num1+Num2 Print(sum) Output: 30 K.ANGURAJU , AP/CSE

2.Relational expression it perform operation by using relational operator. (<, > <= , >= , == ,!=) Example: A=10 B=20 If(A>B): print(“a is big”) Else: print(“b is big”) Output: b is big K.ANGURAJU , AP/CSE

3.Logical expression it perform the operation by using logical operators Example: if((a>b)and (a>c)): 4.Conditional expression Here also we use relational operator to perform conditional operation. K.ANGURAJU , AP/CSE

In python we assign the various values into multiple variable at same time Example: Var1,var2,….. Var n=exp1,exp2…….exp n Example: swapping of two numbers A=11 A,B=11,20 B=20 A,B=B,A Print(“after swapping A and B value is”, A,B)

Data type Description Memory bytes Example int integer numbers 2 bytes int a=20; float Decimal point numbers 4 bytes float b=20.1 char Single character 1 byte char s=n; double Double precision both int and float 8 bytes double d=2343242 232 K.ANGURAJU , AP/CSE

Data type of an variable determines what values it holds and also what operation performed on it. There are following data types are: 1.Integer (int) 2. Floating point type (float) 3. String type (string) 4.Booleans (bool type) 5. List (list []) 6.Tuple (tuple ()) 7.None type (None) K.ANGURAJU , AP/CSE

Integer: An integer type (int ) represents signed whole numbers . without decimal point. They can be positive or negative numbers. The range is -2 , 147 to +2 , 147 1. Normal integer numbers: It is a signed whole numbers it may be positive or negative >>> a = 27 >>> b = -23 >>> c = 3435 K.ANGURAJU , AP/CSE

2. Octal literals (base 8) To indicate integer in octal numbers, you can use the prefix of 0o or 0O(zero followed by upper or lower case o) >>> x = 0o56 >>> print(x) 46) 3. Hexadecimal literals( base 16): To indicate integer in hexadecimal numbers, you can use the prefix 0x or 0X(zero followed by upper or lower case x) >>> y = 0x9A >>> print(y) >>>154 K.ANGURAJU , AP/CSE

4. Binary literals( base 2): To indicate integer in binary numbers, you can use the prefix 0b or 0B(zero followed by upper or lower case b) >>> s = 0b1111 >>> print(s) 15 K.ANGURAJU , AP/CSE

Definition: Floating point type represent numbers with fractional part (or) real numbers with decimal point. They can be positive or negative numbers, It will take 4 bytes of memory. Example: >>> a = 3.14 >>> b = -15.45 K.ANGURAJU , AP/CSE

Strings in python are identified as a nearby set of characters represented in the quotation marks. python allows either pairs of single or double quotes, Ex: ‘Hi’ or “Hello” or ‘“Hi’’’ Slicing in string: subsets of strings can be taken using the slice operator( [] and [:] ) K.ANGURAJU , AP/CSE

Definition Boolean is a data type, Having two values it is denoted by True and False , It is defined by “George Boole” The most common way to produce a Boolean value is with a relational operator >>> print(2==2) True >>> print (2<3) True Print(2!=2) False K.ANGURAJU , AP/CSE

• A list contains items separated by commas and enclosed with square bracket [ ] . • List holds heterogeneous values • List and arrays are same in python. • values stored in list is accessed by using its index or its value by slicing. Syntax List_name=[ ] Or List_name= [ value1, value2 …. Value n] Example 1: >>> a = [ ] - empty list >>> b = [“ram”, 31 , 54 , 12 , 47 ] >>> print( b ) [“ram”, 31 , 54 , 12 , 47] K.ANGURAJU , AP/CSE

tuple contains items(elements) separated by commas and enclosed with parenthesis(). After creation of tuple those values cannot be modified and also cannot insert a new element with in those tuple In tuple also possible to assign more than one values into more than one variable at a time. Example: >>> s=(“ram”, 54 , 656 , 50) >>> print(s) ‘ram’ , 54 , 656 , 50 >>> print(s[0]) ‘ram’ >>> a , b =(10 , 20) >>> print (a,b) >>> 10 20 K.ANGURAJU , AP/CSE

Arithmetic expression are evaluated by using it’s precedence(PEMDAS). When an expression contains more than one operator , then the order of evaluation depends on it’s operator precedence. Parentheses having highest precedence , it is executed first with in the expression. Example: 5*(5+3) = 40 In this expression first execute parenthesis , then multiply with five and produce 40 as result. K.ANGURAJU , AP/CSE

Next highest precedence is exponentiation Next highest precedence is multiplication and division ( * , / , % ) The lowest precedence is addition and subtraction.( + , -) Operator with the same precedence are evaluated from left to right. EXAMPLE: Workout this expression and write correct answer . 3 – 9*(3 + 7)+7 * 3 - 1 K.ANGURAJU , AP/CSE

The value of variable is may change during the execution of a program, But the named constant represents permanent data that never changes. python does not have any special syntax for creating named constant. you can simply create a variable and named as constant. for difference we use upper character letter to a constant variable Example: PI=3.14

Operators An operator is symbol that specifies an operation to be performed on the operands. Types of operator: 1. Arithmetic operator. + , - , / , *, % 2. Relational Operator. 3. Logical Operator. 4. Assignment Operator. 5. Bitwise Operator. 6. Membership Operators 7. Identity Operators K.ANGURAJU , AP/CSE

Arithmetic operators are used to perform mathematical operation like addition , subtraction , division ….etc it require two operands + - addition operator - - Subtraction operator * - multiplication operator / - division operator % - Modulo division operator ** - Exponent (x**y ) K.ANGURAJU , AP/CSE

Example program: a = int ( input (“Enter the a value”)) b= int ( input ( “enter the b value”)) sum = (a + b) print("Sum of two number is :", sum) K.ANGURAJU , AP/CSE

Relational Operator: These operators compare the values on either sides of them and decide the relation among them. They are also known as Relational operators . < - less than <= - less than or equal to >= -greater than or equal to > -greater than = = - is equal to ! = - not equal to K.ANGURAJU , AP/CSE

Example: a= int ( input ( “enter a value”)) b= int (input (“enter b value”)) if (a>b): print(“a is big”) else: print(“b is big”) K.ANGURAJU , AP/CSE

Python logical operator are used to combine two or more conditions and perform the logical operations using Logical AND, Logical OR and Logically NOT. Logical (and ) (a>c) and (a>b) Logical ( or ) (a>b) or (a>d) Logical NOT 29!=29 K.ANGURAJU , AP/CSE

Example: a= int ( input ( “enter a value”)) b= int (input (“enter b value”)) c = int (input (“enter c value”)) if (a>b) and (a>c): print(“a is big”) elif (b>c): print(“b is big”) else: print(“c is big”) K.ANGURAJU , AP/CSE

Assignment operator used assign a values of a variable. Python allows you to combine assignment and addition operation using an augmented assignment operator += Addition assignment -= Subtraction assignment *= Multiplication assignment /= Float division assignment //= integer division assignment **= Exponent assignment K.ANGURAJU , AP/CSE

Syntax: variable= expression or value; Example: a=10 b=20 c= a+b print(“sum of two number is”,c)

Bitwise operator used to manipulate the data at bit level, it operates on integers only. it not applicable to float or real. operator meaning & Bitwise AND | Bitwise OR ^ Bitwise XOR << Shift left >> Shift right ~ One’s complement K.ANGURAJU , AP/CSE

Bitwise AND (&) Here operate with two operand bit by bit. Truth table for & is: x= 7= 0000 0111 y= 8 = 0000 1000 a&b Output: 0000 0000 Bitwise OR ( |) x= 7= 0000 0111 y= 8 = 0000 1000 a I b Output: 0000 1111 Bitwise exclusive OR (^) x= 7= 0000 0111 y= 8 = 0000 1000 & 0 1 0 0 0 1 0 1 | 0 1 0 0 1 1 1 1 ^ 0 1 0 0 1 1 1 0 K.ANGURAJU , AP/CSE

Python’s membership operators test for membership in a sequence, such as strings, lists, or tuples. There are two membership operators as explained below in - Evaluates to true if it finds a variable in the specified sequence and false otherwise. not in - Evaluates to true if it does not finds a variable in the specified sequence and false otherwise K.ANGURAJU , AP/CSE

>>> s1="welcome" >>> for word in s1: print(s1) Output: welcome welcome welcome welcome welcome welcome welcome K.ANGURAJU , AP/CSE

Identity operators compare the memory locations of two objects. There are two Identity operators explained below: is is not Example: x=20 ; y=25 if ( x is not y): print (“different identity”) else: print (“same identity”) K.ANGURAJU , AP/CSE

Example 2: x=15 ; y=20 if ( x is not y): print (“different identity”) else: print (“same identity”) K.ANGURAJU , AP/CSE

Type conversion is the process of convert one data type into another type. if an integer and float are involved in a binary operation, python automatically converts the integer to a float value. This is called type conversion. so 3*4.5 is converted as 3.0 * 4.5 sometimes to convert the float value as integer we use int(value) function.

Example: >>>Value=6.5 >>>Int(value) 6 >>> You can also use round(value) function to round a number to the nearest whole number. >>>value=5.6 >>>round(value) 6

A function is a group of statements that perform a specific task. Python having lot of predefined library functions Ex: eval(), input(), print()…etc These are build in function they are always available in the python interpreter. you don’t have to import any modules to use the functions additionally. Ex: abs, max, min, pow, and round,…etc

Simple python build in function abs(x) - return absolute value for x Ex: abs(-2) >>>2 max(x1,x2) - return largest among x1,x2 Ex:max(10,20) >>>20 min(x1,x2) - return smallest among x1,x2 Ex:min(10,23) >>>10 Pow(a,b) - return a**b value Ex:pow(2,3) >>>8 Round(x) - return an integer nearest to x Ex:round(10.6) >>>11

Mathematical function The python math module provides the mathematical function. listed below sin(x) -returns the sine of x cos(x) - returns the cosine of x tan(x) - returns the tangent of x exp(x) -returns the exponential of x Log(x) -returns the logarithm of x degrees() - convert angle x from radians to degree radians() - converts the angle x from degrees to radians. Example: import math Math.sin(x)

a string is a sequence of character. Python treat strings and character same way. String values must be enclosed in single or double quotes. Python does not have a data type for character. Example: >>>name=“ramkumar” >>>initial=“m”

AscII code a character is stored in a computer as a sequence of 0s and 1s. There are different ways to encode a character. One popular standard is ASCII(American Standard code for Information Interchange) It provide 7 bit encoding scheme for representing all uppercase and lowercase letters, digits, …etc. ASCII uses 0 through 127 to represent character.

Unicode: Python also support Unicode Unicode is an encoding scheme for representing international character. ASCII is small subset of Unicode. Unicode was established by the unicode consortium to support interchange, processing, and display the written text in the word’s diverse language.

Python provides the ord(ch) function for returning the ASCII code for the character ch The chr(ch) function for returning the character represented by the code. Example: >>> ch='a' >>> ord(ch) 97 >>> chr(98) 'b' >>> ord('A') 65 >>>

Python uses special notation, which consist of a backslash (/) followed by a letter or combination of digit. Example: n - linefeed b -Backspace t -Tab -backslash

To print the multiple values or character with in single line using end statement. Example: Print(“ram”, end=“ “) Print(“kumar”, end=‘ ‘) Print(“mani”, end=‘***’) Output: ram kumar ***

this function is used to convert a number into a string. Example: >>>S=str(3.4) >>>Print(s) >>>‘3.4’

UNIT 1 PY .ppt - PYTHON PROGRAMMING BASICS

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UNIT 1 PY .ppt - PYTHON PROGRAMMING BASICS