Python

1. Computer Programming

• Definition: Process of writing a set of instructions to solve real-life problems.

• Programming languages have rules called syntax (like grammar in human languages) while giving the instruction to the computer.

• Examples of programming languages: Python, Java, JavaScript, C, C++.
  
  

2. Introduction to Python

• Python is recommended as the first programming language for beginners as it is simple and easy to learn.

• File extension: .py

• History:

  • Developed by Guido van Rossum in 1989 at the National Research Institute, Netherlands.

  • Released publicly in 1991.

  • Name inspired by the BBC TV show “Monty Python’s Flying Circus”.
    
    

3. Features of Python

• Free and Open-Source – no cost, even for commercial use.

• Cross-platform – works on Windows, macOS, Linux.

• Interpreted Language – executes code line by line.

• Dynamically Typed – variables can change types during runtime.

• Code Optimization – fewer lines of code compared to other languages.

  • Example: Printing “Hello World” in Python requires just one line.
    
    

4. Career Opportunities with Python

• Data Analyst – data collection, processing, and visualization.

• Web Developer – dynamic websites & apps.

• Machine Learning Engineer – building predictive models.

• AI Developer – creating intelligent systems.
  
  

5. Python Text Editor (IDLE)

• IDLE = Integrated Development Learning Environment.

• Installed automatically with Python.

• Used for writing and running Python programs.

• Two modes:

  1. Interactive Mode (Shell) – quick testing and exploration.

  2. Script Mode (Editor) – creating, saving, and reusing full programs.
     
     

6. Using Python IDLE

• Installation: Download from python.org → Check “Add Python to PATH” during installation.

• Creating a file: File → New File → Write code → Save with .py.

• Running a program: Run → Run Module (or press F5).

• Opening an existing file: Right-click file → Edit with IDLE.
  
  

7. Key Points

• Programming - giving instructions to a computer.

• Syntax - rules of a programming language.

• Python - simple, powerful, beginner-friendly.

• .py - file extension for Python programs.

• IDLE - built-in editor (Interactive Mode + Script Mode).

• Careers - Data, Web, AI, ML.

1. Output in Python

• Output: Information or result produced by a computer after input, processing, and storage.

• In Python, print() function is used to display messages, text, numbers, or results on the console/terminal.

2. Syntax of print()

print(object, sep="", end="")

• object → Mandatory (what you want to print).

• sep → Optional (separator between multiple objects, default is space).

• end → Optional (what to print at the end, default is newline \n).
  
  

👉 If the object is a string, enclose it in quotes (' ' or " ").
👉 If the object is a variable, no quotes are needed.

3. Output Formatting

Output formatting makes the displayed result more readable and meaningful.
 

Some of the ways to format output:

1. Comma Operator ( , ) – separates values with a space.
   
   print("Name:", "Karma")   # Output: Name: Karma

2. Plus Operator ( + ) – concatenates (joins) strings.
   
   print("Hello" + " Bhutan")   # Output: Hello Bhutan

3. F-Strings – allows inserting variables/expressions directly inside strings.
   
   name = "Dorji"

print(f"My name is {name}")     # Output: My name is Dorji

1. What is a Variable?

• A variable is a container for storing data values.

• Variables store different data types like:

  • Numbers (integers, floats)

  • Strings (text)

  • Lists, Sets, Tuples, Dictionaries

• Example:
  
  age = 15  --------- storing numbers

name = "Sonam" --------- storing strings

cars = ["Alto", "Prado", "Hilux", "Creta"] ------- a list

2. Importance of Variables

• Data Storage – store values for later use.

• Data Manipulation – use variables in calculations/operations.

• Value Sharing – share data across different parts of a program.

• Data Representation – descriptive variable names make programs clearer.
  
  

3. Rules for Naming Variables

✅ Rules:

• Must begin with a letter or an underscore (_).

• Cannot start with a number.

• Can only contain letters, numbers, and underscores.

• Are case-sensitive (Name and name are different).

• Should be descriptive (use meaningful names).
  
  

❌ Invalid examples:

• 2value, my-name, class

✅ Valid examples:

• age, student_name, _count
  
  

4. Types of Variable Assignment

1. Direct Assignment
   
   x = 10

name = "Karma"

2. Multiple Assignment
   
   x = y = 4     # same value to multiple variables

3. Chained Assignment
   
   x, y, z = 3, 4, 5   # different values to multiple variables

Comments in Python

Comments are lines in code that explain what the code does.

• • • Not executed by the computer.

    • Written for human readers (programmers).

    • Help improve readability, understanding, and collaboration.
      
      

Benefits of Comments:

• Make code easier to understand.

• Act as reminders or explanations.

• Help other programmers when maintaining or updating code.

• Useful in debugging and teamwork.
  
  

Types of Comments:

• • Single-line Comments

    • Start with # (hash symbol).

    • Everything after # on the same line is treated as a comment.

    • Used for short explanations.

Example:

# This code adds two numbers

x = 5 + 10

• • Multi-line Comments

    • Written inside triple quotes (""" ... """).

    • Can span across multiple lines.

    • Used for long explanations, documentation, or describing algorithms.

Example:

"""

This program demonstrates

the use of multi-line comments.

"""

print("Hello World")

Input Function in Python

• • input() is used to get information from the user during program execution.

  • The entered data is always stored as a string (text), even if it looks like a number.

  • Program pauses and waits for the user to type and press Enter.
    
    

Syntax:
variable = input("Message to user: ")

Examples:
name = input("Enter your name: ")

print("Hello", name)

Importance of input():

• • Makes the program interactive.

  • Collects data from the user.

  • Stores user responses in variables.

  • Useful for personalized outputs.

Good programming refers to writing code that is efficient, easy maintainable, and follows best practices to enhance readability.

Common practices:

• • Code testing and debugging

  • Code optimization

  • Code documentation
    
    

Advantages

• Easy to understand

• Less hassle to update/maintain

• Code reuse (modular programming)

• Faster performance

• Clear documentation and reliable testing

Debugging

• Definition: Finding and fixing mistakes (bugs) in a program.

• Like being a “detective” for your code.
  
  

Importance of Debugging:

• Identifies errors in the code

• Improves quality and reliability

• Saves time/resources by catching problems early

• Optimizes performance
  
  

Types of Errors

1. Syntax Error – Mistake in code rules (e.g., missing punctuation, wrong keywords).
   Example: x==”PEMA” instead of x=="PEMA"

2. Semantic Error – Mistake in logic/meaning (code runs but gives wrong results).
   Example: dividing a number by 0.

Code Optimization

• Definition: Improving program performance by reducing execution time and memory usage.

• Techniques:

  • Use efficient algorithms

  • Remove repetitive code

  • Use Python features (multiple assignments, loops, etc.)

Example:

# Multiple assignment

x, y, z = "karma", 24, "Khaling"

print("My name:", x, "Age:", y, "I am from:", z)

Code Documentation

• Definition: Writing explanations inside code for clarity.

• Methods:

  • Comments (inline notes in code)

  • Function documentation (purpose, parameters, return values, exceptions)

  • Usage of examples

Data types represent the types of data present inside a variable. In other words, a data type is like a label that tells the computer what kind of information is stored in a variable. A data type could be a number, a piece of text, or a true/false value.

Data types in programming helps in:

• • Efficient memory usage

  • Preventing errors

  • Improving readability

Classification of Python Data Types

1. Numeric Types

   • int → represents whole numbers (5, -10)

   • float → represents decimals numbers (3.14, -2.5)

   • complex → numbers with real & imaginary parts (4+8j)
     
     

2. Text Type

   • str → represents sequence of characters in quotes (‘ ’, “ ”, or ''' ''')
     
     

3. Sequence Types

   • list → ordered, changeable, in [ ]

   • tuple → ordered, unchangeable, in ( )

   • range → sequence of numbers, often in loops
     
     

4. Mapping Type

   • dict → consists of key-value pairs {“name”: “Pema”}
     
     

5. Set Types

   • set → unordered, { }

   • frozenset → immutable version of a set
     
     

6. Boolean Type

   • bool → True or False (used in conditions)

Strings in Detail

1. Quotes: single('abc'), double("abc"), triple('''abc''')

2. Indexing:

   • Positiveve index (left → right, starts from 0)

   • Negative index (right → left, starts from -1)

3. Slice Operator [start:stop:step]

4. String Operations:

   • Concatenation (+)

   • Repetition (*)

Type Casting

• Converting one data type to another.

• Functions:

  • int(), float(), complex(), str(), bool()

Escape Characters

Special characters inside strings:

• • \n → newline

  • \t → tab space

  • \" → double quote

  • \' → single quote

  • \\ → backslash