slide1
Download
Skip this Video
Download Presentation
STARTING OUT WITH Python First Edition by Tony Gaddis

Loading in 2 Seconds...

play fullscreen
1 / 24

STARTING OUT WITH Python First Edition by Tony Gaddis - PowerPoint PPT Presentation


  • 246 Views
  • Uploaded on

Chapter 5 Repetition Structures. STARTING OUT WITH Python First Edition by Tony Gaddis. 5.1 Introduction to Repetition Structures. Concept: The repetition structure causes a statement or set of statements to execute repeatedly. 5.1 Introduction to Repetition Structures.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' STARTING OUT WITH Python First Edition by Tony Gaddis' - zuzela


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Chapter 5Repetition Structures

STARTING OUT WITH

PythonFirst Edition

by Tony Gaddis

5 1 introduction to repetition structures
5.1 Introduction to Repetition Structures

Concept:

The repetition structure causes a statement or set of statements to execute repeatedly.

5 1 introduction to repetition structures1
5.1 Introduction to Repetition Structures
  • Condition-Controlled and Count-Controlled Loops
  • A condition-controlled loop uses a true/false condition to control the number of times that it repeats.
  • A count-controlled loop repeats a specific number of times.
5 2 the while loop a condition controlled loop
5.2 The while Loop: a Condition-Controlled Loop

Concept:

A condition-controlled loop causes a statement or set of statements to repeat as long as a condition is true. In Python you use the while statement to write a condition-controlled loop.

5 2 the while loop a condition controlled loop1
5.2 The while Loop: a Condition-Controlled Loop
  • In Python …
  • while condition:
  • statement
  • statement
  • etc.

Figure 5-1 The logic of a while loop

5 2 the while loop a condition controlled loop3
5.2 The while Loop: a Condition-Controlled Loop
  • The while Loop is a Pretest Loop, which means it tests its condition before performing an iteration.
5 3 the for loop a count controlled loop
5.3 The for Loop: a Count-Controlled Loop

Concept:

A count-controlled loop iterates a specific number of times. In Python you use the for statement to write a count-controlled loop.

5 3 the for loop a count controlled loop1
5.3 The for Loop: a Count-Controlled Loop
  • In Python …
  • for variable in [value1, value2, etc.]:
  • statement
  • statement
  • etc.
5 3 the for loop a count controlled loop2
5.3 The for Loop: a Count-Controlled Loop
  • Using the range Function with the for Loop
  • for num in [0, 1, 2, 3, 4]:
  • print num
  • for num in range(5):
  • print num
5 3 the for loop a count controlled loop3
5.3 The for Loop: a Count-Controlled Loop
  • Using the range Function with the for Loop
  • for num in range(1, 10, 2):
  • print num
  • First argument, 1, is the starting value for the list
  • Second argument, 10, is the ending limit of the list
  • Third argument, 2, is the step value
5 3 the for loop a count controlled loop4
5.3 The for Loop: a Count-Controlled Loop

Program 5-12 (user_squares2.py)

5 3 the for loop a count controlled loop5
5.3 The for Loop: a Count-Controlled Loop
  • Generating Lists that Range from
  • Highest to Lowest
  • for num in range(5, 0, -1):
  • print num
5 4 calculating a running total
5.4 Calculating a Running Total

Concept:

A running total is a sum of numbers that accumulates with each iteration of a loop. The variable used to keep the running total is called an accumulator.

5 4 calculating a running total1
5.4 Calculating a Running Total
  • Programs that calculate the total of a series of numbers typically use two elements:
  • A loop that reads each number in the series
  • A variable that accumulates the total of the numbers as they are read.
5 4 calculating a running total2
5.4 Calculating a Running Total

Figure 5-7 Logic for calculating a running total

5 4 calculating a running total3
5.4 Calculating a Running Total
  • The Augmented Assignment Operators

Table 5-2 The age variable references the value 25

5 5 sentinels
5.5 Sentinels

Concept:

A sentinel is a special value that marks the end of a sequence of values.

5 6 input validation loops
5.6 Input Validation Loops

Concept:

Input validation is the process of inspecting data that has been input to a program, to make sure it is valid before it is used in a computation. Input validation is commonly done with a loop that iterates as long as an input variable references bad data.

5 6 input validation loops1
5.6 Input Validation Loops
  • Error Trap or Error Handler

Figure 5-8 Logic containing an input validation loop

5 6 input validation loops2
5.6 Input Validation Loops
  • Priming Read
  • # Get a test score.
  • Score = input(‘Enter a test score: ‘)
  • # Make sure it is not less than 0.
  • while score < 0:
  • print ‘ERROR: The score cannot be negative.’
  • score = input (‘Enter the correct score: ‘)
5 7 nested loops
5.7 Nested Loops

Concept:

A loop that is inside another loop is called a nested loop.

5 7 nested loops1
5.7 Nested Loops
  • for hours in range(24):
  • for minutes in range(60):
  • for seconds in range(60):
  • print hours, ‘:’, minutes, ‘:’, seconds
  • About Nested Loops:
  • The inner loop goes through all of its iterations for every single iteration of the outer loop
  • Inner loops complete their iterations faster than outer loops
ad