Mastering Programming in Python Lesson 3(b) All you need to know about FOR LOOPS

Lesson 1: Introduction to the language, SEQUENCE variables, create a Chat bot Lesson 2: Introduction SELECTION (if else statements) Lesson 3a): Introducing ITERATION (While loops) Lesson 3b): Introducing For Loops Lesson 4: Use of Functions/Modular Programming Lesson 5: Introducing Lists /Operations/List comprehension Lesson 6: Use of Dictionaries Lesson 7: String Manipulation Lesson 8: File Handling – Reading and writing to CSV Files Lesson 9: Importing and Exporting Files Lesson 10: Transversing, Enumeration, Zip Merging Lesson 11: Recursion Lesson 12: Project 1 Lesson 13 Project 2 Lesson 14: Project 3 Lesson 15: Consolidation of all your skills – useful resources Series Overview *Please note that each lesson is not bound to a specific time (so it can be taken at your own pace) Information/Theory/Discuss Task (Code provided) Challenge (DIY!) Suggested Project/HW COMING SOON

In this lesson you will …  Learn about loops, specifically the FOR LOOP  Predict the output (For Loop Task)  Adapt and change code involving For Loops  Compare ‘while’ and ‘for’ loops.  Use the break statement and see how it works  Learn about Nested Loops  Create your own For Loops  Create the beginnings of an Arithmetic quiz using a random function and for loops  Big ideas: Is the universe digital? A program?  Introducing Gottfried Leibniz and Konrad Zuse *For this series we assume students know how to open, save and run a python module. Version: Python 3

Did you know? Guido van Rossum, the guy on the right, created python! He is a Dutch computer programmer and completed his degree in the university of Amsterdam He was employed by Google from 2005 until December 2012, where much of his time was spent developing the Python language. In 2013, Van Rossum started working for Dropbox. Python is intended to be a highly readable language. It has a relatively uncluttered visual layout, frequently using English keywords where other languages use punctuation. Guido van Rossum, the creator of Python An important goal of the Python developers is making Python fun to use. This is reflected in the origin of the name which comes from Monty Python

The difference between ‘While’ and ‘For’ For loops are traditionally used when you have a piece of code which you want to repeat n number of times. As an alternative, there is the WhileLoop, however, while is used when a condition is to be met, or if you want a piece of code to repeat forever, for example -WhileLoop For loops are traditionally used when you have a piece of code which you want to repeat n number of times. As an alternative, there is the WhileLoop, however, while is used when a condition is to be met, or if you want a piece of code to repeat forever, for example -WhileLoop For loops are used when the number of iterations are known before hand. The name for-loop comes from the English word “for”, which is used as the keyword in most languages. The term in English dates to ALGOL 58

For Loops and game design … Take, for example, the game ‘Super Mario’. For loops can be used to create a timed interval recall loop for each animation. See if you can spot the “for loop” in the code below. It would be hard to come across a programmed game that has not utilised a for loop of some kind in its code.

The anatomy of a For Loop for in : else: for in : else: The For Loop can step through the items in any ordered sequence list, i.e. string, lists, tuples, the keys of dictionaries and other iterables. It starts with the keyword "for" followed by an arbitrary variable name. This will hold the values of the following sequence object, which is stepped through. Generally, the syntax looks like this:

Task 1: Predict the output (using For Loops) Predict the output, then code it yourself to see if you were right! Both of these do the same thing. Note: 0 is the starting point. Look out for FORMAT SPECIFIERS: The %d specifier refers specifically to a decimal (base 10) integer. The %s specifier refers to a Python string.

Were your predictions right? Answers: This is the Fibonacci sequence!

Nested Loops And now for a Nested Loop. This will break each word into its constituent letters and print them out. A Nested loop is basically a loop within a loop. You can have a for loop inside a while loop or vice versa. Let’s start with something simple. Use a for loop to print out the items in a list. OUTPUT

Challenge 1: 3 and 4 times table up to 10 This bit of code produces the times tables for the numbers 1 and 2 (and only up to 5). Can you change it to produce the following? (3 and 4 times table up to 10) 1.Type in the code below (nested loop used) 2.Run it to see what it does 3.Now try and change the values in the program to get it to do what is required. 4.Once done, play around with these values and get it to produce more timestables! You could go all the way up to 100! 1.Type in the code below (nested loop used) 2.Run it to see what it does 3.Now try and change the values in the program to get it to do what is required. 4.Once done, play around with these values and get it to produce more timestables! You could go all the way up to 100! Desired output

Solution1: 3 and 4 times table up to 10 The key is to understand the way the “range” works in Python. Change the numbers to the following and it should work! Now you can experiment with doing more! Output Change the above to ….

The ‘Break’ statement – how it works! found = False # initial assumption for value in values_to_check() : if is_what_im_looking_for(value) : found = True break #end if #end for #... found is True on success, False on failure found = False # initial assumption for value in values_to_check() : if is_what_im_looking_for(value) : found = True break #end if #end for #... found is True on success, False on failure Having no way out of a situation is never a good thing! In python programming, you can use the ‘Break’ statement to exit a loop – say for instance the conditions of the loop aren’t met.

Note how ‘break’ provides an early exit Having no way out of a situation is never a good thing! In python programming, you can use the ‘Break’ statement to exit a loop – say for instance the conditions of the loop aren’t met. OUTPUT Note only 1,2,3,4 are printed from the range and once x = 5, the loop is exited! OUTPUT? Nothing! This is because the loop finds ‘1’ and breaks before it can do anything! ???????

Challenge 2: Extend the code and get someone to try out your program! 1.Copy the code on the right and analyse how it works (notice use of user input, lists and for loops) 2.Extend the program to: a)Ask the user how many more holidays they are planning for the coming year(s) b)Allow them to enter the places they would like to visit c)Append these new values to the list. d)Print the new list. e)If they enter a number over 10 or zero, exit the loop. 1.Copy the code on the right and analyse how it works (notice use of user input, lists and for loops) 2.Extend the program to: a)Ask the user how many more holidays they are planning for the coming year(s) b)Allow them to enter the places they would like to visit c)Append these new values to the list. d)Print the new list. e)If they enter a number over 10 or zero, exit the loop. print ("**********Hello, welcome to the program***********") print ("This program will ask you to enter the names of places you've been to") print ("Before we get started, please enter the number of places you want to enter") number = int(input("How many holidays have you had this year?: ")) print ("Thank you!") print ("We'll now ask you to enter all the places you've traveled to: ") places_traveled = [] #Empty list created to hold entered values for i in range(number): #range(number) used because we want to limit number of inputs to user choice places = input("Enter Place:") places_traveled.append(places) print (("Here's a list of places you've been to: \n"), places_traveled)

Challenge 3:The beginnings of an Arithmetic Quiz Program. Can you extend it? 1.Copy the code on the right and analyse how it works (notice use of random function and for loops) 2.Extend the program to: a)Create more questions (what would you need to change to do this?) b)Add a division operator to the mix so that the questions also extend to division. c)Gifted and Talented: What else could you add to make this program more interesting? How about a score variable that increments each time an answer is correct? 1.Copy the code on the right and analyse how it works (notice use of random function and for loops) 2.Extend the program to: a)Create more questions (what would you need to change to do this?) b)Add a division operator to the mix so that the questions also extend to division. c)Gifted and Talented: What else could you add to make this program more interesting? How about a score variable that increments each time an answer is correct? # # Name: Maths Quiz # Purpose: Tutorial # Author: teachingcomputing.com # Created: 23/02/2016 # Copyright: (c) teachingcomputing.com 2016 # import random #identifying the variables we will be using score=0 answer=0 operators=("x", "+", "-") #Randomly generate the numbers and operators we will be using in this Maths Quiz #The For in in range loop will tell us how many times to repeat the program for i in range(3): #variable num is equal to a random number between 5 and 10 num1=random.randint(5,10) #this will generate a random number between 1 and 5 num2=random.randint(1,5) #select an operator of choice operator=random.choice(operators) #Now we need to calculate the answer! For that, we need to know which operator is being used if operator=="+": answer=num1+num2 elif operator=="-": answer=num1-num2 elif operator=="x": answer=num1*num2 #Creating the question (randomly generated) and create user's input #remember the lines to follow should be indented to be IN the above for loop print('What is' + str(num1)+operator+str(num2)) user_answer=int(input("Enter Answer: ")) #This section allows for the user's response if user_answer==answer: print("That's Right") else: print("Not quite, sorry! The answer was: " + str(answer)) score=score

Discussion: Is the universe Binary? You may find Wikipedia’s listing on digital universe possibilities an interesting read In physics and cosmology, digital physics is a collection of theoretical perspectives based on the premise that the universe is, at heart, describable by information and is therefore computable. Some scientists say that the universe may in fact be a computer program.

Useful Videos to watch on covered topics What is the nature of the universe we live in? Recommended video on Python For Loops

Suggested Project / HW / Research  Create a research information point on Gottfried Leibniz  Basic facts about him  Achievements  His interpretation and understanding of Binary  How Binary plays a role in computers today!  Write an essay (or create an informational power point) on ‘DO WE LIVE IN A BINARY UNIVERSE?”  What were Konrad Zuse’s views on a Binary/ digital universe  Charles Babbage claimed that miracles were the ‘master programmer’ at work – do you agree?  If there is a God (higher power) might he be a programmer?  What arguments (for and against) a Binary universe can you present?  Create a research information point on Gottfried Leibniz  Basic facts about him  Achievements  His interpretation and understanding of Binary  How Binary plays a role in computers today!  Write an essay (or create an informational power point) on ‘DO WE LIVE IN A BINARY UNIVERSE?”  What were Konrad Zuse’s views on a Binary/ digital universe  Charles Babbage claimed that miracles were the ‘master programmer’ at work – do you agree?  If there is a God (higher power) might he be a programmer?  What arguments (for and against) a Binary universe can you present? Gottfried Leibniz Konrad Zuse

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