python.pptx
- 1. K.M.G COLLEGE OF ARTS AND SCIENCE • DEAPARTMENT OF COMPUTER APPLICATIONS • SUBJECT PYTHON • PROF- U.POORNIMA •
- 2. CHAPTER - IV CONDITIONAL AND ITERATIVE STATEMENTS SELECTION ITERATION
- 5. INTRODUCTION
- 6. INTRODUCTION Programs are written for the solution to the real world problems. A language should have the ability to control the flow of execution so that at different intervals different statements can be executed. Structured programming is a paradigm aims at controlling the flow of execution of statements in a program by using control structures. A language which supports the control structures is called as structured programming language
- 7. TYPES OF CONTROL STRUCTURES
- 8. A Structured programming is an important feature of a programming language which comprises following logical structure: 1. SEQUENCE 2. SELECTION 3. ITERATION OR LOOPING 4. BRANCHING OR JUMPING STATEMENTS TYPES OF CONTROL STRUCTURES
- 9. Sequence is the default control structure; instructions are executed one after another. Statement 1 Statement 2 Statement 3 …….. …….. …….. 1. SEQUENCE
- 10. 1. SEQUENCE – FLOW CHART
- 11. 1. SEQUENCE – FLOW CHART Statement 1 Statement 2 Statement 3
- 12. 1. SEQUENCE - PROGRAM
- 13. Sequence is the default control structure; instructions are executed one after another. # This program adds two numbers def sum_of_two_no(): num1 = 1.5 num2 = 6.3 sum = float(num1) + float(num2) print('The sum is =‘, sum) sum_of_two_no(): 1. SEQUENCE - PROGRAM
- 15. A selection statement causes the program control to be transferred to a specific flow based upon whether a certain condition is true or not. 2. SELECTION
- 16. CONDITIONAL CONSTRUCT – if else STATEMENT
- 17. CONDITIONAL CONSTRUCT – if else STATEMENT Conditional constructs (also known as if statements) provide a way to execute a chosen block of code based on the run-time evaluation of one or more Boolean expressions. In Python, the most general form of a conditional is written as follows: Contd.. Next Slide
- 18. CONDITIONAL CONSTRUCT – if else STATEMENT if first condition: first body elif second condition: second body elif third condition: third body else: fourth body : Colon Must
- 19. CONDITIONAL CONSTRUCT – if else STATEMENT FLOW CHART
- 20. CONDITIONAL CONSTRUCT – if else STATEMENT FLOW CHART Condition ? Statement 1 Statement 2 Statement 1 Statement 2 False True else body Main Body
- 21. CONDITIONAL CONSTRUCT – if else STATEMENT Each condition is a Boolean expression, and each body contains one or more commands that are to be executed conditionally. If the first condition succeeds, the first body will be executed; no other conditions or bodies are evaluated in that case.
- 22. CONDITIONAL CONSTRUCT – if else STATEMENT If the first condition fails, then the process continues in similar manner with the evaluation of the second condition. The execution of this overall construct will cause precisely one of the bodies to be executed. There may be any number of elif clauses (including zero), and The final else clause is optional.
- 23. CONDITIONAL CONSTRUCT – if else STATEMENT EXAMPLE - PROGRAM
- 24. EXAMPLES – if STATEMENT OUT PUT else is missing, it is an optional statement
- 25. CONDITIONAL CONSTRUCT EXAMPLE – if else STATEMENT
- 26. EXAMPLE – if else STATEMENT OUT PUT else is used : Colon Must
- 27. CONDITIONAL CONSTRUCT EXAMPLES – if elif STATEMENT
- 28. EXAMPLES – if elif STATEMENT READ AS 18 is less than age and 18 is less than 60 OUTPUT
- 29. 3. ITERATION OR LOOPING ITERATION
- 30. 3. ITERATION OR LOOPING What is loop or iteration? Loops can execute a block of code number of times until a certain condition is met. OR The iteration statement allows instructions to be executed until a certain condition is to be fulfilled. The iteration statements are also called as loops or Looping statements.
- 31. 3. ITERATION OR LOOPING Python provides two kinds of loops & they are, for loop while loop
- 32. while loop
- 33. while loop A while loop allows general repetition based upon the repeated testing of a Boolean condition The syntax for a while loop in Python is as follows: while condition: body Where, loop body contain the single statement or set of statements (compound statement) or an empty statement. Contd.. : Colon Must
- 34. while loop The loop iterates while the expression evaluates to true, when expression becomes false the loop terminates. while loop FLOW CHART
- 35. while loop – Programming example
- 36. while loop - programs OUTPUT # Natural Numbers generation
- 37. while loop - programs OUTPUT # Calculating Sum of Natural Numbers
- 38. while loop - programs #Generating Fibonacci numbers
- 39. while loop - programs #Generating Fibonacci numbers OUTPUT
- 40. for LOOP
- 41. for LOOP Python’s for-loop syntax is a more convenient alternative to a while loop when iterating through a series of elements. The for- loop syntax can be used on any type of iterable structure, such as a list, tuple str, set, dict, or file Syntax or general format of for loop is, for element in iterable: body
- 42. for LOOP Python’s for-loop syntax is a more convenient alternative to a while loop when iterating through a series of elements. The for- loop syntax can be used on any type of iterable structure, such as a list, tuple str, set, dict, or file Syntax or general format of for loop is, for element in iterable: body
- 43. for LOOP OUTPUT Till the list exhaust for loop will continue to execute.
- 45. for LOOP - range KEYWORD The range() function returns a sequence of numbers, starting from 0 by default, and increments by 1 (by default), and ends at a specified number. range(start, stop, step) for n in range(3,6): print(n) x = range(3, 6) for n in x: print(n) OR
- 46. for LOOP - range KEYWORD OUTPUT #Generating series of numbers
- 47. for LOOP - range KEYWORD OUTPUT #Generating even numbers
- 48. for LOOP – len() FUNCTION
- 49. for LOOP - range KEYWORD # print string character by character OUTPUT
- 50. else statement in loop
- 51. else statement in loop else can be used in for and while loops the else body will be executed as and when the loop’s conditional expression evaluates to false OUTPUT
- 52. 4. BRANCHING OR JUMPING STATEMENTS
- 53. 4. BRANCHING OR JUMPING STATEMENTS Python has an unconditional branching statements and they are, 1. break STATEMENT 2. continue STATEMENT
- 54. 4. BRANCHING OR JUMPING STATEMENTS 1. break STATEMENT Break can be used to unconditionally jump out of the loop. It terminates the execution of the loop. Break can be used in while loop and for loop. Break is mostly required, when because of some external condition, we need to exit from a loop.
- 55. 1. break STATEMENT break causes jump Condition ? Statement 1 break Loop True
- 56. 1. break STATEMENT OUT PUT
- 57. 2. continue STATEMENT The continue statement in Python returns the control to the beginning of the while loop. The continue statement rejects all the remaining statements in the current iteration of the loop and moves the control back to the top of the loop. The continue statement can be used in both while and for loops.
- 58. 2. continue STATEMENT continue causes jump Condition ? Statement 1 continue Loop True Statement n Statements ignored or skipped False
- 59. 2. continue STATEMENT when i value becomes 2 the print statement gets skipped, continue statement goes for next iteration, hence in the out put 2 is not printed
- 60. pass STATEMENT
- 61. pass STATEMENT The pass statement in Python is used when a statement is required syntactically but you do not want any command or code to execute. The pass statement is a null operation; nothing happens when it executes. The pass is also useful in places where your code will eventually go, but has not been written yet (e.g., in stubs for example):
- 62. pass STATEMENT pass in loop pass in loop has no output
- 63. Thank You