inf-bc-w01-python.md

Python 01: Linear Programs.

Introduction: This document presents learning steps for Python 01. In Python 01, you will learn the first elements of Python to build your first interactive linear program. We define a linear program as a flow of sequential instructions without branching and loops. At the end of Python 01, you will be able to implement a program where a user can enter simple input(s) and the program calculates and prints the results as its output.

Note: In Python 01, exercises and examples can be executed using:

1. Online Python Editor OPyEditor: The final program should be stored on your local machine.
2. Local Python Package (see ExtraStep-01): Using BRef-01: Appendix B Python can be installed on your local machine.

Materials:

The activities are designed based on these following references:

• BRef-01: Book, Bill Lubanovic; "Introducing Python: Modern Computing in Simple Packages"; Available here
• ORef-01: Online Tutorial; Charles Severance; "Python for Everybody"; Available here
• OPyEditor: Online Editor for Programming; "Online Python (with shell and file storing functionalities)"; Available here

Path:

Follow the following steps:

Step-01: What is a Program?

Goals:

After taking this step, you will be able to:
	1. understand the concept of (computer and non-computer) programs.
	2. experience your first taste of Python without knowing all the details.

What to Learn?

1. Use BRef-01: Chapter 01 as a reference and discuss the following questions:
   1. What is a general definition of a program? Provide some (none-computer) examples.
   2. What are the main elements of a program?
   3. First Taste of Python: Read section Little Programs and analyze the provided examples.
   4. Consider the following Python program and guess what each program does. Analyze and discuss inputs, behaviour and expected outputs.
      • Note: Certainly there might be some lines that will be impossible to understand fully. The goal is to evaluate your first taste of Python programs and check how intuitive they are. You will be learning all details in later stages.

#Code 01:
words = []
num_str = input("How many words would you like to enter?")
num = int(num_str)
for _ in range(0, num):
	word = input("Next word: ")
  	words.append(word)
print("This is your list of words:", words)

Exercises:

1. Make a small research to understand the meaning of syntax in programming. Give three examples of the programs you have read in BRef-01: Chapter 01.
2. Take each of the given following Python programs and carry out these steps:
   • Write down syntactical elements that are understandable for you.
   • Specify statements that you know (or you can guess) the results of the their execution.
   • Share your lists within your learning group.
   • Discuss what will be the result of the program (without execution).

Note: It is not expected that students understand all the elements of these programs. The main goal is to get a taste of Python programs and discuss about them. Trust your intuition.

#Code 02f
a = 16
b = 12
b = a
a = 22
print(a)
print(b)
# what will be printed here?

#Code 03
num = int(input("Enter a number: "))
if num < 0:
   print("Enter a positive number")
else:
   sum = 0
   while(num > 0):
       sum += num
       num -= 1
   print("Result is", sum)

#Code 04
import random
print(random.randint(0, 9))

#Code 05
my_str = input("Enter a string: ")
words = [word.lower() for word in my_str.split()]
words.sort()
print("The sorted words are:")
for word in words:
	print(word)

3. Using OPyEditor try to execute the given programs. Does the output of the programs match your expectations?

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Step-02: Everything starts with Data.

Goals:

After taking this step, you will be able to:
	1. understand the general concepts of computer hardware: Hard disk, RAM, CPU, IO.
	2. understand value, variable, primitive data types (int, str, float, boolean).
	3. understand the concept of mutability (some data types are mutable and some are not).
	4. implement Python programs containing: variables, assigning values, print.

What to Learn?

1. Using BRef-01: Chapter 02 explore the answers for the following questions:

Note: There are some concepts (like objects, classes, references) that students may not be able to grasp completely. The main idea is to try as much as possible. They will be more clear later when they learn Object Oriented programming in Python.

1. What is a value? What is a variable?
2. What is a type? Provide five examples.
3. How can you define a variable in Python?
4. Define some variables in Python that are not permitted in Python. Experiment with breaking various rules in defining variables. Analyze the error message.
5. How can you assign a value to a variable? How can we express that two items are equal?
6. How can you identify the type of a value / variable?
7. Perform a free (re)-search and answer the following questions:
   1. What are the character and string types in Python? Make examples.
   2. You have learned how to print something as an output of your program. How can you read something as input? What is the function? What is the type?

Exercises:

1. Check the following program and write down what will be the result of the prints:

x = 12
y = 15
z = 1
y = z
z = 12
y = 13
x = y
y = x
z = 7
print(x)
print(y)
print(z)

2. A phone number is a number. Yet we would want to save it as a text. Can you think of a reason why?
3. The number in the address of your house, for example Kerkweg 8, is a number. Yet we would want to save it as a text. Can you think of a reason why?
4. What is an example from a number we use in the real world that we do want to save as a number in Python, not as a text.
5. User input in Python is always considered a text, even if we just enter numbers; why would it act like this?
6. Define a variable called zipcode (postcode) and give it the value of your own zipcode. Print it using print().
7. Define a variable called favorite_food, give it the value "Pizza". Print it. Change the value to "Roti". Print it.
8. Finish all the exercises listed in BRef-01-Chapter 02: Things to Do.

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Step-03: How to Calculate?

Goals:

After taking this step, you will be able to:
	1. understand the main arithmetic operations in Python.
	2. implement arithmetic expressions in Python.
	3. convert one primitive data type to another using functions: int(), float(), str(), bool().
	4. implement Python programs containing: input from the user, type conversion, calculation, printing.

What to Learn?

1. Using BRef-01: Chapter 03 answer the following questions:
   1. Name basic built-in data types in Python. Use examples.
   2. What are the basic arithmetic operations? Make a list with the meaning (semantics) of each operation.
   3. Why is precedence an important concept? Make examples.
   4. How can you convert one data type to another? Name basic built-in functions.

Exercises:

1. Create two variables with a number in it, you can decide which numbers, add them together and print the result.
2. Do the same for subtraction, division and multiplication.
3. Get input from the user. Save it as a number. Print it.
4. Try to divide something by zero. Describe the error you get.
5. Create two variables with text in them. Print them togeter at once, using only print statement.
6. Python uses PEMDAS. What is that and is it different from the way you learned it?
7. Create one calculation using at least four parentheses, three multiplications and four subtractions. Print the result.
8. Finish all the exercises listed in BRef-01-Chapter 03: Things to Do.

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Learning Activities:

Code Analysis

1. Analyze the programming solutions given below and write down in one sentence: what do they do? What problems do they try to solve?

# Code Analysis 1
# Inputs
a = int(input("enter value A: "))
b = int(input("enter value B: "))

# Processing
t = a
a = b
b = t

# Outputs
print("A =", a)
print("B =", b)

# Code Analysis 2

# Inputs
num = int(input("Enter a number: "))

# Processing
dig = num % 10

# Outputs
print(dig)

2. Implementing a solution for a given problem is challenging for a beginner programmer. It is helpful to have a guideline with some steps. Check this guideline and apply it the Problem 5 of this week. Hint: A template with some examples provided here

3. One of the students has tried to apply the guideline for a given problem. But, the code does not produce the expected results. Check the code and without executing the code try to find the mistake.

# Ask the user for the name of item X.
# Then ask the user for the price of item X.
# Finally, ask the user for desired quantity of item X.
# Based on input, calculate how much you have to pay.
# Write the message in the form:
#   "To purchase N units of X you must pay M euros."


# Inputs
name = input("Input the name of item X: ")

price = input("What is the price of", name, "? ")

quantity = input("How many units of", name, "do you want to buy? ")

# Processing
total = price * quantity

# Outputs
print("To purchase", quantity, "units of", name, "you must pay", total, "euros.")