Python Lecture 5

Python Lecture 5

• 1.
  Creative Commons License Thiswork is licensed under a Creative Commons Attribution 4.0 International License. BS GIS Instructor: Inzamam Baig Lecture 5 Fundamentals of Programming
• 2.
  Iteration Updating variables: Updating avariable by adding 1 is called an increment >>> x = x + 1 Subtracting 1 is called a decrement >>> x = x - 1
• 3.
  The while statement n= 5 while n > 0: print(n) n = n - 1 print('Blastoff!') 1. Evaluate the condition, yielding True or False. 2. If the condition is false, exit the while statement and continue execution at the next statement. 3. If the condition is true, execute the body and then go back to step 1.
• 4.
  The body ofthe loop should change the value of one or more variables so that eventually the condition becomes false and the loop terminates If there is no iteration variable, the loop will repeat forever, resulting in an infinite loop
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  Infinite loops n =10 while True: print(n, end=' ') n = n - 1 print('Done!') While this is a dysfunctional infinite loop, we can still use this pattern to build useful loops
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  Break Statement while True: line= input('> ') if line == 'done': break print(line) print('Done!')
• 7.
  Continue Statement while True: line= input('> ') if line[0] == '#': continue if line == 'done': break print(line) print('Done!')
• 8.
  For Loops Sometimes wewant to loop through a set of things such as a list of words, the lines in a file, or a list of numbers departments = ['BS', 'GIS', 'KIU'] for department in departments: print('Department Name:', department) print('Done!')
• 9.
  Loop Patterns Often weuse a for or while loop to go through a list of items or the contents of a file Or looking for something such as the largest or smallest value of the data we scan through
• 10.
  Loop Patterns These loopsare generally constructed by: • Initializing one or more variables before the loop starts • Performing some computation on each item in the loop body, possibly changing the variables in the body of the loop • Looking at the resulting variables when the loop completes
• 11.
  Counting Items count =0 for itervar in [3, 41, 12, 9, 74, 15]: count = count + 1 print('Count: ', count)
• 12.
  Counting and summingloops total = 0 for itervar in [3, 41, 12, 9, 74, 15]: total = total + itervar print('Total: ', total)
• 13.
  Maximum and Minimum largest= None print('Before:', largest) for itervar in [3, 41, 12, 9, 74, 15]: if largest is None or itervar > largest : largest = itervar print('Loop:', itervar, largest) print('Largest:', largest)
• 14.
  Maximum and Minimum smallest= None print('Before:', smallest) for itervar in [3, 41, 12, 9, 74, 15]: if smallest is None or itervar < smallest: smallest = itervar print('Loop:', itervar, smallest) print('Smallest:', smallest)