{"id":386,"date":"2020-07-07T19:58:02","date_gmt":"2020-07-07T19:58:02","guid":{"rendered":"https:\/\/aaidm.buas.nl\/?page_id=386"},"modified":"2020-08-27T19:15:22","modified_gmt":"2020-08-27T19:15:22","slug":"pr1-preparation-for-week-5-loop-control","status":"publish","type":"page","link":"https:\/\/aaidm.buas.nl\/?page_id=386","title":{"rendered":"PR1 – Preparation for Week 6 – Loop Control"},"content":{"rendered":"\n
\n
Author:<\/td>Carlos Santos<\/td><\/tr>
Learning Line:<\/td>Programming<\/td><\/tr>
Course:<\/td>PR1: Introduction to Programming<\/td><\/tr>
Week:<\/td>4<\/td><\/tr>
Competencies:<\/td>Students will be able to effectively define and use variables, programming flow control.<\/td><\/tr>
BoKS:<\/td>\u00ad 3bK2, The student understands the principles of data related software like Python, R, Scala and\/or Java and knows how to write (basic) scripts.<\/td><\/tr>
Learning Goals:<\/td>Variables and Data Types
In-code Comments<\/td><\/tr><\/tbody><\/table><\/figure>\n<\/div><\/div>\n\n\n\n

Flow Control – while loop<\/h2>\n\n\n\n

If statements help you choose is a set of instructions are performed. There is a similar structure, that not only checks if a set of instructions are performed, but, also repeats them while a specific condition is True<\/em>.<\/p>\n\n\n\n

A while <\/em>loop used a simple condition to determine if a set of instructions are executed, and while that condition is True<\/em>, it keeps repeating the instructions.<\/p>\n\n\n\n

a = 0                                    # declare a variable a and set it to 0\nwhile a < 10:                            # repeat the following operations while a is less than 10\n    print("a current value is "+str(a))  # print value of a\n    a = a + 1                            # increment the value of a        \nprint("a final value is "+str(a))        # exit the loop and print the final value of a<\/pre><\/div>\n\n\n\n
Explanation<\/strong>: The while loop repeats lines 3 and 4, while the condition (a is less than 10)  remains True<\/em>.<\/p>\n\n\n\n
There are a few important things to keep in mind: <\/p>\n\n\n\n
  1. while <\/em>loops are only executed if the condition is True<\/em> to start with;<\/li>
  2. while <\/em>create a new scope, and it repeats the execution of this scope while the condition remains True<\/em>;<\/li>
  3. typically while <\/em>loops manipulate the condition inside of its scope;<\/li>
  4. if the condition its always True<\/em> the loops will continue indefinitely, until it is interrupted externally (for example by forcing application to exit)<\/li><\/ol>\n\n\n\n
    Lets make a simple command line application, that accepts commands, until an “exit” command is typed, by the user.<\/p>\n\n\n\n
    command = ""\nwhile command.lower() != "exit":\n    command = input(">").lower()\n    if command == "hi":\n        print("Hello")\n    elif command == "name":\n        print("Robot")\nprint("Bye")<\/pre><\/div>\n\n\n\n
    Lets elaborate on this concept to introduce a few more concepts. During a loop you can exit by calling the break<\/code> command. break<\/code><\/code> forces the script to abort what it was doing and forces to exit the loop without checking the condition.<\/p>\n\n\n\n
    command = ""\nwhile command.lower() != "exit":\n    command = input(">").lower()\n    if command == "hi":\n        print("Hello")\n    elif command == "name":\n        print("Robot")\n    elif command == "quit" or  command == "bye":\n        break\nprint("Bye")<\/pre><\/div>\n\n\n\n
    There is another command called continue<\/code> which forces the script to restart the loop in the current state (including the condition) and ignoring the follow up code.<\/p>\n\n\n\n
    command = ""\nwhile command.lower() != "exit":\n    command = input(">").lower()\n    if command == "hi":\n        print("Hello")\n    elif command == "name":\n        print("Robot")\n    elif command == "quit" or  command == "bye":\n        break\n    elif command == "?":\n        print("Please type a command.") \n        continue\n        print("DEAD CODE: because this line is preceded by a continue") \nprint("Bye")<\/pre><\/div>\n\n\n\n
    For Loop<\/h2>\n\n\n\n
    Of the loop types listed above, Python only implements the last: collection-based iteration. At first blush, that may seem like a raw deal, but rest assured that Python\u2019s implementation of definite iteration is so versatile that you won\u2019t end up feeling cheated!<\/p>\n\n\n\n
    Shortly, you\u2019ll dig into the guts of Python\u2019s for<\/code> loop in detail. But for now, let\u2019s start with a quick prototype and example, just to get acquainted.<\/p>\n\n\n\n
    Python\u2019s for<\/code> loop looks like this:<\/p>\n\n\n\n
    for <var> in <iterable>:\n    <statement(s)>\n<\/pre><\/div>\n\n\n\n
    <iterable><\/code> is a collection of objects\u2014for example, a list or tuple. The <statement(s)><\/code> in the loop body are denoted by indentation, as with all Python control structures, and are executed once for each item in <iterable><\/code>. The loop variable <var><\/code> takes on the value of the next element in <iterable><\/code> each time through the loop.<\/p>\n\n\n\n
    Here is a representative example:<\/p>\n\n\n\n
    >>> a = ['foo', 'bar', 'baz']\n>>> for i in a:\n      print(i)\nfoo\nbar\nbaz<\/pre><\/div>\n\n\n\n
    The range()<\/code> Function<\/h3>\n\n\n\n
    For example, if you wanted to iterate through the values from\u00a00<\/code>\u00a0to\u00a04<\/code>, you could simply do this:<\/p>\n\n\n\n
    >>> for n in (0, 1, 2, 3, 4):\n       print(n)\n\n0\n1\n2\n3\n4\n<\/pre><\/div>\n\n\n\n
    This solution isn\u2019t too bad when there are just a few numbers. But if the number range were much larger, it would become tedious pretty quickly.<\/p>\n\n\n\n
    Happily, Python provides a better option\u2014the built-in range()<\/code> function, which returns an iterable that yields a sequence of integers.<\/p>\n\n\n\n
    range(<end>)<\/code>\u00a0returns an iterable that yields integers starting with\u00a00<\/code>, up to but not including\u00a0<end><\/code>:<\/p>\n\n\n\n
    >>> for n in range(4):\n       print(n)\n\n0\n1\n2\n3\n4\n<\/pre><\/div>\n\n\n\n
    Range is actually mode elaborate than that. range(<begin>, <end>, <stride>)<\/code>\u00a0returns an iterable that yields integers starting with\u00a0<begin><\/code>, up to but not including\u00a0<end><\/code>. If specified,\u00a0<stride><\/code>\u00a0indicates an amount to skip between values (analogous to the stride value used for string and list slicing):<\/p>\n\n\n\n
    range(<end>)<\/code> returns an iterable that yields integers starting with 0<\/code>, up to but not including <end><\/code>:<\/p>\n\n\n\n
    >>> for n in range(10,5,-2):\n       print(n)\n10\n8\n6<\/pre><\/div>\n","protected":false},"excerpt":{"rendered":"
    Author: Carlos Santos Learning Line: Programming Course: PR1: Introduction to Programming Week: 4 Competencies: Students will be able to effectively define and use variables, programming flow control. BoKS: \u00ad 3bK2, The student understands the principles of data related software like Python, R, Scala and\/or Java and knows how to write (basic) scripts. Learning Goals: Variables […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":99,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-386","page","type-page","status-publish","hentry"],"yoast_head":"\nPR1 - Preparation for Week 6 - Loop Control - Applied Artificial Intelligence and Data Management<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/aaidm.buas.nl\/?page_id=386\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"PR1 - Preparation for Week 6 - Loop Control - Applied Artificial Intelligence and Data Management\" \/>\n<meta property=\"og:description\" content=\"Author: Carlos Santos Learning Line: Programming Course: PR1: Introduction to Programming Week: 4 Competencies: Students will be able to effectively define and use variables, programming flow control. 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