Python basics

Question 1

What is a variable in Python?

Answer 1

A variable is a symbolic name that stores data in memory. It allows you to refer to the value later in the code.
Example:
x = 10
name = “Alice”

Question 2

What are the main data types in Python?

Answer 2

the main data types include int (integer), float (decimal), str (string), bool (boolean), list, tuple, dict (dictionary), and set.

Question 3

How do you comment code in Python?

Answer 3

Use # for single-line comments, and triple quotes ‘’’ or “”” for multi-line comments.
Example:
# This is a single-line comment
“””
This is a
multi-line comment
“””

Question 4

What does type() do in Python?

Answer 4

type() returns the data type of a variable or value.
Example:
print(type(10)) # Output: <class ‘int’>

Question 5

How do you create a list in Python?

Answer 5

A list is created using square brackets [] and can hold multiple data types.
Example:
fruits = [“apple”, “banana”, “cherry”]

Question 6

What is the difference between a list and a tuple?

Answer 6

A list is mutable (changeable), while a tuple is immutable (cannot be changed after creation).
Example:
my_list = [1, 2, 3]
my_tuple = (1, 2, 3)

Question 7

How do you access a dictionary value by key?

Answer 7

Use square brackets with the key name to access the corresponding value.
Example:
person = {“name”: “Alice”, “age”: 25}
print(person[“name”]) # Output: Alice

Question 8

What is a set in Python?

Answer 8

A set is an unordered collection of unique elements.
Example:
my_set = {1, 2, 3, 3}
# Output: {1, 2, 3}

Question 9

Explain an if statement in Python.

Answer 9

An if statement checks a condition and executes the code block if the condition is True.
Example:
x = 10
if x > 5:
print(“x is greater than 5”)

Question 10

What is a for loop used for in Python?

Answer 10

A for loop iterates over a sequence (like a list, tuple, or string) and executes a code block for each element.
Example:
for fruit in [“apple”, “banana”, “cherry”]:
print(fruit)

Question 11

What is the purpose of a while loop?

Answer 11

A while loop repeats a block of code as long as a specified condition is True.
Example:
count = 0
while count < 5:
print(count)
count += 1

Question 12

How do you define a function in Python?

Answer 12

Use the def keyword followed by the function name and parentheses. Code inside the function is indented.
Example:
def greet(name):
print(“Hello, “ + name)

Question 13

What is the purpose of the return statement in a function?

Answer 13

return exits the function and optionally returns a value to the caller.
Example:
def add(x, y):
return x + y

Question 14

Explain the difference between local and global variables.

Answer 14

Local variables are defined within a function and cannot be accessed outside of it, while global variables are defined outside functions and can be accessed anywhere in the code.

Question 15

What are list comprehensions?

Answer 15

List comprehensions provide a concise way to create lists based on existing iterables, often with conditions.
Example:
squares = [x**2 for x in range(10)]

Question 16

what is the difference between yield and return

Answer 16

return
Exits the function immediately, returning a single value or object.
Memory Usage: Stores the entire result in memory, which can be inefficient for large data.
Example:

def get_numbers():
return [1, 2, 3, 4, 5]
yield
Pauses the function, saving its state, and returns a value temporarily.
Returns a generator: Allows handling one item at a time, ideal for large data.
Example:

def get_numbers():
for i in range(1, 6):
yield i
Summary
return: Exits the function with a single result.
yield: Pauses, returns items one by one, making it memory-efficient for large data.

Question 17

What is a generator in Python?

Answer 17

A generator is a function that yields values one at a time and allows you to iterate through them without storing the entire sequence in memory.
Example:
def count_up_to(n):
count = 1
while count <= n:
yield count
count += 1

Question 18

How do you add an element to a list?

Answer 18

Use append() to add an element to the end, or insert(index, element) to add it at a specific position.
numbers = [1, 2, 3]
numbers.append(4) # [1, 2, 3, 4]
numbers.insert(1, 10) # [1, 10, 2, 3, 4]

Question 19

How do you remove duplicates from a list?

Answer 19

Convert the list to a set and back to a list.
Example:
items = [1, 2, 2, 3]
unique_items = list(set(items)) # [1, 2, 3]

Question 20

What is a tuple, and how is it different from a list?

Answer 20

A tuple is an immutable, ordered sequence. Unlike lists, tuples cannot be modified after creation.

Question 21

How can you access elements in a tuple?

Answer 21

Use indexing, similar to lists.
Example:
my_tuple = (1, 2, 3)
print(my_tuple[0]) # Output: 1

Question 22

How do you access a value in a dictionary?

Answer 22

Use the key in square brackets or the get() method.
Example:
person = {“name”: “Alice”}
print(person[“name”]) # Output: Alice

Question 23

How do you remove a key-value pair from a dictionary?

Answer 23

Use pop(key) or del statement.
Example:
person.pop(“age”)
del person[“name”]

Question 24

What is a set in Python?

Answer 24

An unordered collection of unique elements, defined with {}.

Question 25

How do you add elements to a set?

Answer 25

Use add() for a single element, or update() for multiple elements.
Example:
my_set = {1, 2}
my_set.add(3) # {1, 2, 3}
my_set.update([4, 5]) # {1, 2, 3, 4, 5}

Question 26

What is the difference between union() and intersection() methods in sets?

Answer 26

union() combines elements from both sets, while intersection() returns only common elements.

Question 27

How do you reverse a list in Python?

Answer 27

You can use the reverse() method (modifies the list in place) or slice notation.
lst = [1, 2, 3, 4]
lst.reverse() # In-place modification
# or
reversed_lst = lst[::-1] # Slicing

Question 28

How do you sort a list of tuples based on the second element in each tuple?

Answer 28

Use the sorted() function with a custom key.
Example:
data = [(1, ‘apple’), (3, ‘banana’), (2, ‘cherry’)]
sorted_data = sorted(data, key=lambda x: x[1]) # Sort by second element

Question 29

How do you concatenate two lists in Python?

Answer 29

Use the + operator or extend() method.
Example:
list1 = [1, 2]
list2 = [3, 4]
combined = list1 + list2 # [1, 2, 3, 4]
# or
list1.extend(list2) # [1, 2, 3, 4]

Question 30

How do you merge two dictionaries in Python?

Answer 30

Use the update() method or dictionary unpacking (Python 3.5+).
Example:
dict1 = {“a”: 1, “b”: 2}
dict2 = {“c”: 3, “d”: 4}
dict1.update(dict2) # dict1 is now {“a”: 1, “b”: 2, “c”: 3, “d”: 4}
# or
merged_dict = {**dict1, **dict2} # Python 3.5+

Question 31

What happens when you use a mutable object (like a list) as a dictionary key?

Answer 31

It will raise a TypeError because dictionary keys must be immutable (hashable).
Example:
my_dict = {[“a”, “b”]: 1} # Raises TypeError: unhashable type: ‘list’

Question 32

How do you iterate over both keys and values in a dictionary?

Answer 32

Use items() to loop through key-value pairs.
Example:
my_dict = {“a”: 1, “b”: 2}
for key, value in my_dict.items():
print(key, value)

Question 33

How do you find the difference between two sets?

Answer 33

Use the difference() method or the - operator.
Example:
a = {1, 2, 3}
b = {2, 3, 4}
diff = a.difference(b) # {1}
# or
diff = a - b # {1}

Question 34

How do you find the symmetric difference between two sets?

Answer 34

Use symmetric_difference() or ^ operator to find elements in either set but not in both.
Example:
a = {1, 2, 3}
b = {3, 4, 5}
sym_diff = a.symmetric_difference(b) # {1, 2, 4, 5}
# or
sym_diff = a ^ b # {1, 2, 4, 5}

Question 35

What is the difference between shallow copy and deep copy?

Answer 35

A shallow copy duplicates the outer object, but references nested objects, while a deep copy duplicates both the outer and nested objects.
Example:
import copy
original = [[1, 2], [3, 4]]
shallow = copy.copy(original)
deep = copy.deepcopy(original)

Question 36

How do you remove an item from a list by its index?

Answer 36

se the del statement or the pop() method.
Example:
lst = [1, 2, 3, 4]
del lst[2] # Removes element at index 2
lst.pop(1) # Removes element at index 1 and returns it

Question 37

How do you remove an element from a list by value, not index?

Answer 37

Use the remove() method to remove the first occurrence of a value.
Example:
lst = [1, 2, 3, 4]
lst.remove(3) # [1, 2, 4]

Question 38

What are list slicing and how do you use it to reverse a list?

Answer 38

List slicing allows you to access a range of elements in a list. To reverse a list, you use [::-1].
Example:
lst = [1, 2, 3]
reversed_lst = lst[::-1] # [3, 2, 1]

Question 39

How do you check if all elements in a list are unique?

Answer 39

Convert the list to a set and compare its length to the original list’s length.
Example:
lst = [1, 2, 3]
unique = len(lst) == len(set(lst)) # True

Question 40

How do you get a dictionary’s keys, values, and items?

Answer 40

Use keys(), values(), and items() methods.
Example:
my_dict = {“a”: 1, “b”: 2}
keys = my_dict.keys() # dict_keys([‘a’, ‘b’])
values = my_dict.values() # dict_values([1, 2])
items = my_dict.items() # dict_items([(‘a’, 1), (‘b’, 2)])

Question 41

How would you sort a dictionary by its values?

Answer 41

Use sorted() with a custom key function.
Example:
my_dict = {“a”: 3, “b”: 1, “c”: 2}
sorted_by_value = sorted(my_dict.items(), key=lambda x: x[1]) # [(‘b’, 1), (‘c’, 2),

Question 42

How do you find the intersection of two sets?

Answer 42

Use the intersection() method or the & operator.
Example:
set1 = {1, 2, 3}
set2 = {2, 3, 4}
intersection = set1 & set2 # {2, 3}

Question 43

How can you check if a set is a subset of another set?

Answer 43

Use the issubset() method or the <= operator.
Example:
set1 = {1, 2}
set2 = {1, 2, 3}
print(set1.issubset(set2)) # True
print(set1 <= set2) # True

Question 44

What are the advantages of using a generator over a list?

Answer 44

enerators are memory-efficient because they yield values one at a time and don’t store the entire sequence in memory. They also allow for lazy evaluation, which means values are generated only when needed.
Example:
def count_up_to(n):
count = 1
while count <= n:
yield count
count += 1

gen = count_up_to(5)
for num in gen:
print(num) # Outputs: 1, 2, 3, 4, 5

Question 45

What is the difference between deepcopy() and copy()?

Answer 45

Copy() performs a shallow copy, while deepcopy() creates a completely new object, including all nested objects.
Example:
import copy
obj = {“a”: [1, 2]}
shallow = copy.copy(obj)
deep = copy.deepcopy(obj)