Day 1 Python 2024

Syntax

Python syntax is designed to be readable and straightforward. Here are some key points:

1. Indentation: Python uses indentation to define code blocks. Consistent use of 4 spaces per indentation level is the norm.

    if True:
        print("Hello, World!")
    >>Hello, World!
   

2. Comments: Use # for single-line comments and triple quotes for multi-line comments.

    # This is a single-line comment
    """
    This is a
    multi-line comment
    """
   

3. Statements: Python typically uses one statement per line.

    a = 1
    b = 2
    c = a + b
   

Data Types

Python supports various data types, including:

1. Numeric Types:

   • int (e.g., 5)

   • float (e.g., 3.14)

   • complex (e.g., 1 + 2j)

2. Sequence Types:

   • str (e.g., "Hello")

   • list (e.g., [1, 2, 3])

   • tuple (e.g., (1, 2, 3))

3. Mapping Type:

   • dict (e.g., {"name": "Alice", "age": 25})

4. Set Types:

   • set (e.g., {1, 2, 3})

   • frozenset (immutable set)

5. Boolean Type:

   • bool (e.g., True, False)

6. None Type:

   • None

Variables

Variables in Python are dynamically typed. You don't need to declare them before using them.

x = 10
y = 3.14
name = "Alice"

Loops

Python supports two main types of loops: for and while.

1. For Loop:

    for i in range(5):
        print(i)
   
    >>0
    1
    2
    3
    4
    5
   

2. While Loop:

    count = 0
    while count < 5:
        print(count)
        count += 1
    >>0
    1
    2
    3
    4
   

3. Loop Control Statements:

   • break: Exits the loop

   • continue: Skips the current iteration and proceeds to the next

   • pass: Does nothing; a placeholder for future code

    for i in range(10):
        if i == 5:
            break
        print(i)
    >>0
    1
    2
    3
    4

Functions

Functions are defined using the def keyword. They can take parameters and return values.

1. Defining Functions:

    def greet(name):
        return f"Hello, {name}!"
   
    print(greet("Alice"))
   
    >>Hello, Alice!
   

2. Default Arguments:

    def greet(name="Guest"):
        return f"Hello, {name}!"
   
    print(greet())
    print(greet("Bob"))
   
    >>Hello, Guest!
    >>Hello, Bob!
   

3. Variable-Length Arguments:

    def add(*args):
        return sum(args) #Sum is built-in function
   
    print(add(1, 2, 3))
    >>6
   

4. Keyword Arguments:

    def display_info(**kwargs):
        for key, value in kwargs.items():
            print(f"{key}: {value}")
   
    display_info(name="Alice", age=25, city="New York")
   
    >>name: Alice
    age: 25
    city: New York
   

5. Lambda Functions:

    add = lambda x, y: x + y
    print(add(2, 3))
   
    >>5
   

Key Points for Interviews

• Understanding List Comprehensions:

    squares = [x**2 for x in range(10)]#list has[]
    print(squares)
    >>[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
  

• Working with Dictionaries:

    student = {"name": "John", "age": 20}#Dictionary has {}
    print(student["name"])
    >>John
  

• Handling Exceptions:

    try:
        result = 10 / 0
    except ZeroDivisionError:
        print("Cannot divide by zero!")
  
    >>Cannot divide by zero!
  

• Understanding Python's Object-Oriented Programming:

    class Person:
        def __init__(self, name, age):
            self.name = name
            self.age = age
  
        def greet(self):
            return f"Hello, my name is {self.name}."
  
    alice = Person("Alice", 30)
    print(alice.greet())
  

• File I/O Operations:

    with open('sample.txt', 'w') as file:
        file.write('Hello, world!')
  
    with open('sample.txt', 'r') as file:
        content = file.read()
        print(content)
  

Familiarizing yourself with these concepts and practicing coding problems can help you prepare effectively for Python-related interview questions.