> For the complete documentation index, see [llms.txt](https://kgisl.gitbook.io/lab3003/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://kgisl.gitbook.io/lab3003/units/unit2-illustrative2-notes.md).

# Notes for Unit 2 - Illustrative programs

## Program 1

## Source Code

```python
print("Enter two values to swap")
a = int(input())
b = int(input())

# using a temporary variable
print("Swapping using temporary variable...")
t = a
a = b
b = t

print("Value of a is {a} and\nValue of b is {b}".format(a=a, b=b))

# using XOR operator, eliminating the need for 3rd variable
print("Swapping using XOR operator...")
a = a ^ b
b = a ^ b
a = a ^ b

print("Value of a is {a} and\nValue of b is {b}".format(a=a, b=b))


def swap_func():
    global a, b
    print("swap_func function called")
    a, b = b, a


swap_func()  # a and b values get swapped again
print("Value of a is {a} and\nValue of b is {b}".format(a=a, b=b))
```

## Sample Output

![out1](https://i.imgur.com/LNV3850.jpg)

## Demo

run `python3 swap.py` in <https://repl.it/@ashokb/unit-2-illustrative-programs>

## Program2

## Source Code

```python
def circulate(a, b, c):
    i = 3
    while i:
        t = a
        a = b
        b = c
        c = t
        print(a, b, c)
        i -= 1

print("Enter 3 values")
a, b, c = input().split()
print()
circulate(a, b, c)

def circulate_list(alist):
    i = len(alist)
    while i:
        first = alist.pop(0)
        alist.append(first)
        print(*alist, sep=", ")
        i -= 1

alist = input("enter multiple values\n").split()
print()
circulate_list(alist)
```

## Sample Output

![out2](https://i.imgur.com/iSSVEUi.jpg)

## Demo

run `python3 circulate.py` in <https://repl.it/@ashokb/unit-2-illustrative-programs>

## Program 3

<table><thead><tr><th>Question</th><th>Answer</th></tr></thead><tbody><tr><td><p><strong>Coordinate Geometry Terms</strong></p><p><br></p><p>Coordinate Geometry Definition - It is one of the branches of geometry where the position of a point is defined using coordinates.</p><p><br></p><p>What are the Coordinates?</p><p><br></p></td><td><p>What are the Coordinates?</p><p><br></p><p>Coordinates are a set of values which helps to show the exact position of a point in the coordinate plane.</p></td></tr><tr><td><p>Coordinate Plane Meaning - A coordinate plane is a 2D plane which is formed by the intersection of two perpendicular lines known as the x-axis and y-axis.</p><p><br></p><p>What is the <strong>Distance Formula</strong>?</p></td><td><p>What is the Distance Formula?</p><p><br></p><p>It is used to find the distance between two points situated in <strong>A(x1,y1)</strong> and <strong>B(x2,y2)</strong></p><p><br></p></td></tr><tr><td><p>What is the most logical way to represent a cartesian point in Python?</p><p><br></p><p>A. Use two variables, for e.g. x1 and y1 or x2 and y2</p><p>B. Use a single tuple variable</p><p>C. <strong>None</strong> of the above</p></td><td><p><strong>Choice B.</strong></p><p><strong>Tuple</strong> is the logical way of representing a point in Python.</p></td></tr><tr><td><p>What is the <a href="https://en.wikipedia.org/wiki/Syntax_(programming_languages)">syntax</a> for defining a point <code>(3, 4)</code> as a tuple in Python?</p><p><br></p><p>A. <code>(3, 4)</code></p><p>B. <code>tuple(3, 4)</code></p><p>C. Both the above are valid</p></td><td><p><strong>Choice C.</strong></p><p><br></p><p><strong>(3, 4)</strong> and <strong>tuple(3, 4)</strong> are equivalent to each other.</p><p><br></p></td></tr><tr><td><p>How can you deconstruct a <strong>tuple</strong> that represents a point?</p><p><br></p></td><td><p>How do you deconstruct a tuple?</p><p><br></p><p>If</p><p><code>pointA = (6, 8) # construction</code></p><p><br></p><p>then</p><p><code>x1, y1 = pointA # deconstruction</code></p><p><code>print(x1, y1) # 6, 8</code></p></td></tr><tr><td><p><code>x1, y1, x2, y2 = (1, 2, 3, 4)</code></p><p><br></p><p>What is the value of <code>x1</code> and <code>y2</code>?</p></td><td><pre><code>1 and 4. 
</code></pre></td></tr><tr><td><p>What is the distance between (4, 0) and (0, 0)?</p><p><br></p><p><img src="https://memcode-production.s3.us-west-2.amazonaws.com/1585923947937" alt="" data-size="original"></p></td><td><p><strong>4</strong></p><p><br></p><p><code>d = (x1 - x2)</code></p><p><code>= 4 - 0</code></p><p><code>= 4</code></p></td></tr><tr><td><p>What is the distance between (4, 3) and (4, 0)?</p><p><br></p><p><br></p><p><img src="https://memcode-production.s3.us-west-2.amazonaws.com/1585924803590" alt="" data-size="original"></p></td><td><p><strong>3</strong></p><p><br></p><p><code>d = (x1 - x2) + (y1 - y2)</code></p><p><code>= (4 - 4) + (3 - 0)</code></p><p><code>= 0 + 3</code></p><p><code>= 3</code></p></td></tr><tr><td><p>What is the distance between (4, 3) and (0, 0)?</p><p><br></p><p><img src="https://memcode-production.s3.us-west-2.amazonaws.com/1585924993650" alt="" data-size="original"></p></td><td><p>Using previous formula, we get</p><p><br></p><p><code>d = (x1 - x2) + (y1 - y2)</code></p><p><code>= (4 - 0) + (3 - 0)</code></p><p><code>= 4 + 3</code></p><p><code>= 7</code></p><p><br></p><p>But we know from <a href="https://www.mathsisfun.com/algebra/distance-2-points.html">https://www.mathsisfun.com/algebra/distance-2-points.html</a></p><p><br></p><p><img src="https://memcode-production.s3.us-west-2.amazonaws.com/1585925436666" alt="" data-size="original"></p><p><br></p></td></tr><tr><td><p>If (x1 - x2) + (y1 - y2) is giving a higher value than what is correct,</p><p><br></p><p>What can the <strong>distance formula</strong> be?</p></td><td><p>Why not square the x component and square the y component, and then reduce it down by using square root?</p><p><br></p><p>The distance formula is as follows:</p><p><br></p><p><img src="https://memcode-production.s3.us-west-2.amazonaws.com/1585939313392" alt="" data-size="original"></p></td></tr><tr><td>What is the distance between <strong>(2, -1)</strong> and <strong>(5, 3)</strong>?</td><td><img src="https://memcode-production.s3.us-west-2.amazonaws.com/1585926241096" alt="" data-size="original"></td></tr><tr><td><p>Are you confident of writing the code for <strong>Distance between Two Points?</strong></p><p><br></p><p></p></td><td>Test yourself at <a href="http://j.mp/twoPoints">http://j.mp/twoPointsCC</a></td></tr></tbody></table>

## Source Code

```python
from math import sqrt


def distance_between(pointA, pointB):
    x1, y1 = pointA
    x2, y2 = pointB

    distx = x1 - x2
    disty = y1 - y2

    return sqrt(distx**2 + disty**2)


# main program
# tuple packing allows for assigning
# multiple inputs in one statement
print("Enter coordinates for Point A")
pointA = int(input()), int(input())

print("Enter coordinates for Point B")
pointB = int(input()), int(input())

print("distance between {0} and {1} is {2}"
    .format(pointA, pointB, distance_between(pointA, pointB))
)
```

## Sample Output

![out3](https://i.imgur.com/jGNMaNN.jpg)

## Demo

run `python3 distance.py` in <https://repl.it/@ashokb/unit-2-illustrative-programs>

## Teaching Assets

| item                         | link                                                                                                           | remarks                                                                                   |
| ---------------------------- | -------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------- |
| Video capture                | <http://j.mp/distanceThisVideo>                                                                                | demonstrates how to use Memcode and CyberDojo and Slides                                  |
| Memcode cards                | [https://www.memcode.com/courses/2288/](https://www.memcode.com/courses/2288/review)                           | useful for classroom and personal review                                                  |
| CyberDojo link               | <http://cyberdojo1.kgfsl.com/kata/edit/Tx2Vqt>                                                                 | The super simple testing framework for capturing incremental coding sessions              |
| Google Slides                | [PDF version](https://github.com/kgisl/pythonFDP/blob/master/units/Unit%202%20-%20illustrative%20programs.pdf) | Or PPTx file is better?                                                                   |
| Auto-generated documentation | [distance\_between](/lab3003/docs.md#distance_between) doctstring documentation                                | consolidates all docstrings in one place ([docs/README.md](/lab3003/docs.md)) in the repo |

## Bonus Material

### Swap

There are actually 4 ways to do it. Please find all of them. <https://www.geeksforgeeks.org/python-program-to-swap-two-variables/>