Paper 4 General TIPS

What function is used to open a file in Python?

open(filename, mode)

What mode should you use to read a file?

'r' (read mode)

What mode should you use to write to a file?

'w' (write mode, overwrites existing content)

What mode should you use to append to a file?

'a' (append mode, adds to existing content)

How do you read all lines from a file at once?

file.readlines()

How do you write a list of strings to a file?

file.writelines(list_of_strings)

How do you initialize an empty list in Python?

my_list = []

How do you declare a 2D array in Python?

my_array = [[0] * cols for _ in range(rows)]

How do you append an item to a list?

my_list.append(item)

How do you insert an element at a specific position in a list?

my_list.insert(index, item)

How do you remove an element from a list?

my_list.remove(item) or my_list.pop(index)

What is a linked list?

A data structure where elements (nodes) are connected using pointers.

How do you define a node in a linked list in Python?

class Node: def __init__(self, data): self.data = data; self.next = None

What is a head node in a linked list?

The first node of the linked list.

What does a linked list node store?

A data value and a pointer to the next node.

What value is used to indicate the last node in a linked list?

-1 or None (depends on implementation).

How do you define a class in Python?

class ClassName: followed by a constructor.

What is a constructor method in Python?

__init__(self, parameters) initializes an object.

What is encapsulation?

Restricting direct access to object attributes (use private variables).

How do you define a private attribute in Python?

Prefix it with self.__attribute_name.

What is a getter method?

A method that returns the value of a private attribute.

What is a circular queue?

A queue where the last position connects to the first.

How do you check if a circular queue is full?

If (Tail + 1) % size == Head.

How do you add an item to a circular queue?

Using an enqueue() function.

How do you remove an item from a circular queue?

Using a dequeue() function.

What is a function in Python?

A reusable block of code that performs a task.

How do you define a function in Python?

def function_name(parameters):

What does the return keyword do?

It sends back a value from a function.

What is the difference between return and print?

return gives a value back, print just displays it.

How do you pass parameters by reference in Python?

Mutable objects (lists, dicts) are passed by reference automatically.

What sorting algorithm is best for small lists?

Insertion Sort or Bubble Sort.

What is the time complexity of QuickSort?

O(n log n) on average.

How does Binary Search work?

It divides the sorted array in half and searches recursively.

What is the worst-case time complexity of Linear Search?

O(n)

What is the advantage of Merge Sort?

It's stable and works well for large datasets.

How do you handle errors in Python?

Using try-except blocks.

What does the except block do?

Catches and handles exceptions.

What exception is raised for division by zero?

ZeroDivisionError

What exception is raised for accessing a non-existent list index?

IndexError