pyq1

1. Python Numeric Data Types

1. Definition: Numeric data types in Python are used to store numeric values such as integers, floating-point numbers, and complex numbers.

2. Types supported:

3. int - Definition: Represents whole numbers without decimal points. - Features: Unlimited size, positive or negative. - Syntax/Example:

a = 42
b = -5

4. float - Definition: Represents real numbers with decimal points. - Features: Double-precision floating-point format. - Syntax/Example:

pi = 3.14159
temp = -45.6

5. complex - Definition: Represents complex numbers with real and imaginary parts. - Features: Imaginary part denoted with ‘j’. - Syntax/Example:

z = 3 + 4j

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2. Iterative Statements in Python

1. Definition: Statements that repeatedly execute a block of code while a condition holds or over a sequence.

2. Types:

3. while loop - Syntax:

while condition:
    # code block

    - Example:

count = 0
while count < 5:
    print(count)
    count += 1

4. for loop - Syntax:

for variable in sequence:
    # code block

    - Example:

for i in range(5):
    print(i)

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3. Exception in Python

1. Definition: An exception is an event that occurs during program execution which disrupts the normal flow of instructions.
2. Features:
   • Handled using try-except blocks.
   • Can be built-in or user-defined.
3. Common standard exceptions:

No.	Exception	When Raised
1	ArithmeticError	Failed numeric calculations
2	ZeroDivisionError	Division or modulo by zero
3	AttributeError	Attribute reference fails
4	EOFError	Unexpected end of input
5	ImportError	Failure to import module
6	IndexError	Sequence index out of range
7	KeyError	Missing dictionary key
8	NameError	Identifier is not found
9	TypeError	Inappropriate operation on type
10	ValueError	Argument has correct type but invalid value

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4. Variable Number of Arguments in Functions

1. Definition: Allows a function to accept arbitrary number of positional or keyword arguments.
2. Syntax and usage:
   • *args: tuple of positional arguments.
   • **kwargs: dictionary of keyword arguments.
3. Example:

def example(*args, **kwargs):
    print("Positional:", args)
    print("Keywords:", kwargs)
 
example(1, 2, 3, name="John", age=30)

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5. Objects and Functions in Python

1. Objects:
   • Everything in Python is an object that contains data (attributes) and functionality (methods).
   • Example: Strings, lists, functions are all objects.
2. Functions:
   • Defined using the def keyword.
   • Are first-class objects: can be assigned, passed, and returned.
   • Example:

def greet():
    print("Hello!")
 
func = greet  # assign function to variable
func()        # call through variable

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6. Lists and Tuples

1. List:
   • Definition: Mutable ordered collection.
   • Syntax: my_list = [1][2][3]
   • Features: Items can be changed, added, removed.
2. Tuple:
   • Definition: Immutable ordered collection.
   • Syntax: my_tuple = (1, 2, 3)
   • Features: Items cannot be changed; safer for fixed data.
3. Differences:

Feature	List	Tuple
Mutability	Mutable	Immutable
Syntax	[ ]	( )
Performance	Slower	Faster
Methods	More (append, remove)	Fewer

4. Use case example:

fruits = ['apple', 'banana']
coordinates = (10.0, 20.0)  # fixed location

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7. Short Notes

1. Iterators

Definition

• An iterator is an object that enables traversing through all the elements of a container (like list, tuple) one at a time.
• Provides a way to access elements sequentially without exposing the underlying structure.

Key Features

• Implements two special methods: __iter__() and __next__().
• __iter__() returns the iterator object itself and is called once at the start of iteration.
• __next__() returns the next element in the sequence and advances the iterator.
• When no more elements are available, __next__() raises StopIteration exception to signal the end.

Syntax & Example

class MyNumbers:
    def __iter__(self):
        self.a = 1   # Initialize starting position
        return self
 
    def __next__(self):
        x = self.a
        self.a += 1  # Move to next number
        if x > 5:    # Stop after 5
            raise StopIteration
        return x
 
my_iter = iter(MyNumbers())
 
print(next(my_iter))  # Output: 1
print(next(my_iter))  # Output: 2
# and so on until 5, then StopIteration is raised

Usage Notes

• You mostly do not create iterators manually; instead, use Python’s iter() function and for loops that implicitly use iterators.
• Example iterating a list:

my_list = [10, 20, 30]
it = iter(my_list)                   # Get iterator
print(next(it))  # 10
print(next(it))  # 20
print(next(it))  # 30
# next(it) now raises StopIteration

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2. Lambda Expressions

Definition

• An anonymous, small inline function defined with the keyword lambda.
• Useful for short, throwaway functions without a formal def block.

Features

• Can take any number of arguments but only a single expression.
• Automatically returns the result of the expression.
• Commonly used with functions like map(), filter(), sorted(), or as callbacks.

Syntax

lambda arguments: expression

Examples

square = lambda x: x * x
print(square(5))  # Output: 25
 
add = lambda x, y: x + y
print(add(3, 4))  # Output: 7
 
# Using lambda with map()
numbers = [1, 2, 3, 4]
squares = list(map(lambda x: x*x, numbers))
print(squares)  # Output: [1, 4, 9, 16]

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3. Range Function

Definition

• Generates a sequence of integers, commonly used for looping a defined number of times.

Features

• Returns an iterable sequence starting from start (inclusive) to stop (exclusive) with step increments.
• Default start is 0, and default step is 1.

Syntax

range(stop)
range(start, stop[, step])

Examples

for i in range(5):
    print(i)
# Output: 0 1 2 3 4
 
for i in range(2, 10, 2):
    print(i)
# Output: 2 4 6 8

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4. Function Decorators

Definition

• A decorator is a function that modifies or enhances the behaviour of another function without modifying its source code.
• Applied with @decorator_name syntax above the target function definition.

Features

• Takes a function as input and returns a new function, usually a wrapped version.
• Used for logging, access control, timing, caching, etc.

Syntax

def decorator(func):
    def wrapper():
        # Code before function call
        func()
        # Code after function call
    return wrapper
 
@decorator
def say_hello():
    print("Hello!")

Example

def uppercase_decorator(func):
    def wrapper():
        result = func()
        return result.upper()
    return wrapper
 
@uppercase_decorator
def greet():
    return "hello world"
 
print(greet())  # Output: HELLO WORLD

Explanation

• The greet function is passed to uppercase_decorator.
• The returned wrapper function calls original greet(), modifies its output, and returns the modified result.
• When calling greet(), the decorated version runs.

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8. Python Matrix Addition Program (with Validation)

def input_matrix(rows, cols):
    matrix = []
    for i in range(rows):
        row = input(f"Row {i+1} values: ").split()
        if len(row) != cols:
            raise ValueError("Incorrect number of columns")
        matrix.append([int(x) for x in row])
    return matrix
 
def add_matrices(a, b):
    return [[a[i][j] + b[i][j] for j in range(len(a[0]))] for i in range(len(a))]
 
r = int(input("Rows: "))
c = int(input("Cols: "))
 
try:
    matrix1 = input_matrix(r, c)
    matrix2 = input_matrix(r, c)
    result = add_matrices(matrix1, matrix2)
 
    print("Matrix 1:")
    for row in matrix1:
        print(row)
    print("Matrix 2:")
    for row in matrix2:
        print(row)
    print("Result:")
    for row in result:
        print(row)
except Exception as e:
    print("Error:", e)

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9. Fraction Class with Arithmetic

class Fraction:
    def __init__(self, numerator=0, denominator=1):
        self.numerator = numerator
        self.denominator = denominator
 
    def set_fraction(self, numerator, denominator):
        self.numerator = numerator
        self.denominator = denominator
 
    def get_fraction(self):
        return f"{self.numerator}/{self.denominator}"
 
    def add(self, other):
        num = self.numerator * other.denominator + other.numerator * self.denominator
        den = self.denominator * other.denominator
        return Fraction(num, den)
 
    def subtract(self, other):
        num = self.numerator * other.denominator - other.numerator * self.denominator
        den = self.denominator * other.denominator
        return Fraction(num, den)

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10. Fibonacci Series Function and Print

def fibonacci(m):
    a, b = 0, 1
    if m == 1:
        return a
    elif m == 2:
        return b
    for _ in range(3, m+1):
        a, b = b, a + b
    return b
 
n = int(input("Number of terms: "))
for i in range(1, n+1):
    print(fibonacci(i), end=" ")

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11. File Reading: Count Characters, Words, Lines

filename = input("Enter filename: ")
 
try:
    with open(filename, 'r') as f:
        content = f.read()
        characters = len(content)
        words = len(content.split())
        f.seek(0)
        lines = len(f.readlines())
 
    print("Characters:", characters)
    print("Words:", words)
    print("Lines:", lines)
except FileNotFoundError:
    print("Error: File not found.")