Python Classroom notes 24/Aug/2024

Importance of Operating Systems

• Operating Systems make it easier to communicate with hardware devices
• Operating Systems runs applications and to make this happen they create process
• Each Process gets some cpu and to preserve any data it uses disks
• Generally application are stored on a disk, when we want to execute the application, OS creates a process

Datatypes

• Purpose of datatypes is to specify the size of data to be allocated in memory and also make it easy for developers
• Two types of Data
  • Fixed Length
  • Variable Length
• To make it easier for developers there will be basic datatypes around the type of data
  • numeric
    • integer
    • decimal numbers
  • boolean
  • text
    • character
    • string
  • custom datatypes
    • structures

int a = 10;
float b = 10.56;

• Programming languages are further categorized into two types based on how the approach datatypes
  • static typed languages: We need to specify to type of data (C,C++, Java, C#, typescript)
    • we need to store balance amount in memory float balance = 1000.59
  • dynamic typed languages: During the code execution, language will allocate the type depeneding on the values passed (Javascript, python, bash/shell)
    • we need to store balance amount in memory balance = 1000.59

Problem solving with Flora

• Selfie
  
• Flora expects a sequence of instructions and it executes them line by line
• Flora remembers anything with an alias

Remember 10 as number
or
number = 10

• Flora knows basic arthimetic

+
-
*
/  10/3 = 3
% remainder 10%3 == 1

• Flora knows comparisions

<
<=
==
>
>=

• While writing instructions lets have line numbers added

Area of Rectangle

• Instructions

1. Hello Flora
2. Remember 10 as length
3. Remeber 40 as breadth
4. calculate length * breadth and remember as result
5. display result

Perimeter of Rectangle

• Instructions

1. Hello Flora
2. Remember 10 as length
3. Remeber 40 as breadth
4. calculate length + breadth and store in result (result = length + breadth)
5. calculate result * 2 and store in result (result = result * 2)
6. display result

Area of circle

• Instructions

1. Hello flora
2. Remember 3.14 as pi
3. Remember 10 as radius
4. result = pi * radius * radius
5. display result

Find if the number is even or odd

• Instructions

1. Hello flora
2. Remember 10 as number
3. remainder = number % 2
4. if remainder == 0 say even
5. if remainder == 1 say odd

• Conditional statements (tip)
  • if
  • if else
  • if else if
  • switch/case

Find the students grade

• Flora learnt how to combine statements using and or
• Problem
  
• Lets give flora the average or percentage and make her say the grade
• Instructions

1. Hello flora
2. Remember 10 as average
3. if average >= 90 and average <= 100 
    3.1. say Excellent
4. if avergage >= 80 and average < 90
    4.1 say Good
5. if avergage >= 65 and average < 80
    5.1 say Fair
6. if avergage >= 55 and average < 65
    6.1 say Poor
7  if average < 55
    7.1 say Very Poor

• Lets print line number execute according to different values of average
  • 100: 1 -> 2 -> 3 -> 3.1 -> 4 -> 5 -> 6 -> 7 Excellent
  • 65: 1 -> 2 -> 3 -> 4 -> 5 -> 5.1 -> 6 -> 7 Fair
• The instructions above will make flora work even after finding the grades
• Instructions

1. Hello flora
2. Remember 10 as average
3. if average >= 90 and average <= 100 
    3.1. say Excellent
    3.2 go to line 8
4. if avergage >= 80 and average < 90
    4.1 say Good
    4.2 go to line 8
5. if avergage >= 65 and average < 80
    5.1 say Fair
    5.2 go to line 8
6. if avergage >= 55 and average < 65
    6.1 say Poor
    6.2 go to line 8
7  if average < 55
    7.1 say Very Poor
8. Bye

• Lets print line number execute according to different values of average
  • 100: 1 -> 2 -> 3 -> 3.1 -> 3.2 -> 8 Excellent
  • 65: 1 -> 2 -> 3 -> 4 -> 5 -> 5.1 -> 5.2 -> 8 Fair
• Consider boundary conditions i.e. allow only valid set of values

1. Hello flora
2. Remember 10 as average
3. if average > 100 or average < 0
   3.1 Say give me right averages
...
...

Find the total of 4 digit number

• Examples

1234 => 1 + 2 + 3 + 4 => 10 => 1 + 0 => 1
353 => 3 + 5 + 3 => 11 => 2

• Break larger problem into smaller problems
  • Take digits out 12 => 2 (12%10 = 2, 12/10 = 1)
• Instructions

1. Hello Flora
2. Remember 82 as number
3. Remember 0 as result
4. digit = number % 10 
5. number = number / 10
6. result = digit + result
7. if number > 0 
    7.1 go to 4
8. if result > 9
    8.1 number = result
    8.2 result = 0
    8.3 go to 4
9. say result

• Tip: Looping constructs help in executing block (sequence of lines) multiple times according to conditions, generally in most languages we have
  • while
  • for

Find if the number is pallendrome or not

• A number is conisdered pallendrome if the reverse is equal to original number

121 => 121  (Pallendrome)
123 => 321 ( not a pallendrome)

• Write instructions

1. Hello Flora
2. Remember 353 as number
3. Remember 0 as reverse
4. original = number
5. digit = number % 10
6. number = number / 10
7. reverse = reverse * 10 + digit
8. if number > 0
    8.1 go to line number 5
9. if original == reverse
    9.1 say pallendrom
10. if original != reverse
    10.1 say not a pallendrome

• Subtitution: As discussed in the classroom