Python Programming. Introduction Part II

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1 Python Programming Introduction Part II

2 Type Conversion One data type > another data type Example: int > float, int > string. >>> a = 5.5 >>> b = int(a) >>> print(b) 5 >>>> print(a) 5.5 Conversion from int to float and stored at b but original value does not change.

3 Types of Conversion q Implicit Type Conversion q Explicit Type Conversion Ø Implicit Type conversion or automatic type conversion Automatically converts one data type to another type num_int = 123 num_float = 2.35 new_num = num_int + num_float print(new_num) output: print(type(new_num)) < class float >

4 Explicit conversion Example: num_int = 234 num_str = 100 print(num_int + num_str) output: TypeError: unsupported operand type(s) for +: int and str This is because python can not do implicit conversion in such condition.

5 Explicit conversion User converts the data type of an object to required data type using predefined data types. This process is called typecasting Syntax: Required_datatype (Expression) Example: num_int = 234 num_str = 100 num_str = int(num_str) print(num_int + num_str) Output: 334

6 Python Input, Output and Import Python has many built-in functions to perform I/O tasks. Examples: abs() > returns absolute value of a number. abs(-5) > 5. int() > returns integer from a number or string. int(3.5) > 3 input() > standard input print() > standard output

7 q Input() Input() function gets data from the user. Syntax of Input(): input([prompt]) prompt is the screen we want to display in the screen. num = input( Enter a number: ) Enter a number: 5 print(num) 5

8 q Output() print() is used to output data to standard output. Examples: print( Welcome to class ) output: Welcome to class x = 100 print(x) output: 100

9 By default python s print function ends with a newline. C/C++ programmer may wonder how to print without newline. print( welcome to seminar, end = ) welcome to seminar print( welcome to seminar, end ) print( UTEP ) welcome to UTEP Print(5,5,sep= * ) 5*5

10 Output Formatting Output formatting can be done using str.format() method. a = 5; b = 6 print( The value of a is {} and b is {}.format(a,b)) The value of a is 5 and b is 6 print( I love {1} {0}.format( programming, python )) I love python programming print( The value of a is %d %a) The value of a is 5

11 Arithmetic operators: Operators in Python Operators are special symbols in python used for arithmetic and logical computation. The values that the operator operates on are called operands + operator > addition >>> Other Examples: -, *, / %, //, ** %, modulus operator returns the remainder of the division. // Floor division- returns the whole number adjusted to the left in the number line. Example: 2//3 0

12 Comparison Operators Used to compare the results ==, Eaual to - True if both operands are equal. >, <, ==,!=, <=, >= a =10 b = 11 print(a>b) False

13 Logical Operators Logical operators are the and, or, not operators. Operator Meaning Example and True if both the operands are true x and y or True if either of the operands is true x or y not True if operand is False. not x x = True y = False print(x or y) True Other operators: Bitwise operators, Assignment operators and special operators such as Identity operators, Membership operators.

14 Namespace and Scope What is Name in python? Name is just a name or identifier given to an object. Example x = 3 3 is an object and x is a name. What is Namespace? Namespace is a collection of names. It s a container that holds the objects and names associated to those objects. Types of Namespace and scope Built-in Namespace Module: Global Namespace Function: Local Namespace

15 Scope Rules in Python: LEGB All computer languages have scope rules LEGB rule in Python is summarized as 1. Local 2. Enclosing Built-in 3. Global 4. Built-in Global Enclosing Local

16 Local Scope Local scope is always first Global scope is searched after the local and enclose a = 5 print(a) a is declared in global scope. However, a name must be defined before it is used print(a) a = 5 NameError: name a is not defined.

17 a = 50 def func1(): global d c = 'number d = 100 def func2(): b = 55 print(a,b) func2() func1() print(d) Output: Example

18 Example a = 50 def func1(): #global d c = 'number d = 100 def func2(): b = 55 print(a,b,d) func2() func1() Print(d) Output: NameError: name 'd' is not defined

19 Enclosing Scope Functions can be nested. Search order: Local >>> Enclosing scopes >>> global scope If a name is not found in above using above order, then the built-in names are searched. Built-in names can be found as: >>> dir( builtins )

20 Quizes 1) a = 10.5 b = int(a) print(b) 10 2) x= El Paso y = Texas print(x + y) El PasoTexas print(a)? 10.5

21 3) a = 50 def func1(): func1() print(b) Output: b = 100 print(a+b) NameError: name 'b' is not defined 4) a = 50 def func1(): global b b = 100 print(a+b) func1() print(b)

22 Thank you Questions?

Chapter 4 : Informatics Practices. Data Handling. Class XI ( As per CBSE Board) Visit : python.mykvs.in for regular updates

Chapter 4 : Informatics Practices Class XI ( As per CBSE Board) Data Handling Introduction Most of the computer programming language support data type, variables,operator and expression like fundamentals.python