Python Quiz: 100 MCQ Questions for Interview Prep (2026)

1What is the output of: print(type([1, 2] * 0))?

Answer: <class 'list'>

💡 Explanation: Multiplying a list by 0 yields an empty list []. The type of an empty list remains a list, so print(type([])) outputs <class 'list'>.

2What is the output of the following code:

def func(a, b=[]):
    b.append(a)
    return b

print(func(1))
print(func(2))

Answer: [1] and [1, 2]

💡 Explanation: Default arguments in Python are evaluated once when the function is defined, not when it is called. The mutable default list `b` is shared across calls. The first call appends 1, and the second call appends 2 to the same list.

3Which of the following is used to manage resources like file streams safely in Python, even if exceptions occur?

Answer: with statement (context managers)

💡 Explanation: The `with` statement utilizes context managers (implementing __enter__ and __exit__ magic methods) to guarantee cleanup operations (like closing files or database connections) are executed.

4What is the output of the following dictionary operation:

d = {1: "a", 1.0: "b"}
print(d[1])

Answer: b

💡 Explanation: In Python, 1 and 1.0 hash to the exact same value, and they compare as equal (1 == 1.0). Since keys must be unique, the entry for 1.0 overrides the value for 1, resulting in d[1] returning "b".

5How does Python handle memory management under the hood?

Answer: Automatic garbage collection using reference counting and a cyclic garbage collector

💡 Explanation: Python uses reference counting as its primary mechanism (deallocating objects when refcount hits 0) supplemented by a generational garbage collector to identify and clear reference cycles.

6What is the output of the following list comprehension:

nums = [1, 2, 3]
print([x * y for x in nums for y in [0, 1] if x > 1])

Answer: [0, 2, 0, 3]

💡 Explanation: The outer loop filters x > 1, retaining 2 and 3. For 2, y = [0, 1] yields 0 and 2. For 3, y = [0, 1] yields 0 and 3. Combining these yields the flat list: [0, 2, 0, 3].

7What is the difference between a shallow copy and a deep copy in Python (copy module)?

Answer: Shallow copy copies references of nested objects; deep copy recursively copies values of nested objects.

💡 Explanation: `copy.copy()` constructs a new compound object and inserts references to the original nested elements. `copy.deepcopy()` recursively copies nested objects, preventing changes to the copied object from affecting the original.

8What is the purpose of the __init__ method in a Python class?

Answer: It acts as a constructor to initialize instance attributes when an object is instantiated.

💡 Explanation: `__init__` is an instance initializer called automatically after the object is created by `__new__` to bind initial state variables to the `self` object.

9What is the output of the following generator expression:

gen = (x for x in range(3))
print(list(gen))
print(list(gen))

Answer: [0, 1, 2] and []

💡 Explanation: Generators in Python are iterators that exhaust their values upon consumption. The first `list(gen)` call consumes all values (0, 1, 2). The second call finds the generator exhausted, returning an empty list [].

10What is the main limitation of the Global Interpreter Lock (GIL) in CPython?

Answer: It prevents multiple native threads from executing Python bytecodes at once (restricting CPU-bound multi-threading).

💡 Explanation: The GIL is a mutex protecting access to Python objects to prevent race conditions. It restricts execution of Python bytecodes to one thread at a time, limiting multi-threaded performance on multi-core processors. CPU-bound performance is optimized using multiprocessing or native C extensions.

11What is the difference between a list and a tuple?

Answer: Lists are mutable (changeable); tuples are immutable (fixed).

💡 Explanation: Lists use [] and can be modified after creation. Tuples use () and cannot be changed, which makes them hashable and usable as dictionary keys.

12What is the difference between "is" and "==" in Python?

Answer: "==" compares values; "is" compares identity (same object in memory).

💡 Explanation: a == b checks whether the values are equal. a is b checks whether both names refer to the exact same object.

13Are Python strings mutable?

Answer: No, strings are immutable.

💡 Explanation: Once created, a string cannot be changed in place. Methods like .upper() return a new string rather than modifying the original.

14What is the output of bool("")?

Answer: False

💡 Explanation: An empty string is "falsy". Empty containers ('', [], {}, ()), 0, and None all evaluate to False in a boolean context.

15What is the difference between the "/" and "//" operators?

Answer: "/" is float division; "//" is floor (integer) division.

💡 Explanation: 7 / 2 gives 3.5, while 7 // 2 gives 3, flooring the result to the nearest lower whole number.

16What is the output of "3" * 3?

Answer: '333'

💡 Explanation: Multiplying a string by an integer repeats it, so "3" * 3 concatenates the string three times.

17What is the difference between a set and a list?

Answer: A set is unordered and stores only unique elements; a list is ordered and allows duplicates.

💡 Explanation: Sets remove duplicates automatically and offer fast membership tests, but do not support indexing.

18What does the None keyword represent?

Answer: The absence of a value (a null object).

💡 Explanation: None is a singleton representing "no value". It is the default return value of a function without a return statement.

19How do you check the type of a variable?

Answer: Using type() or isinstance().

💡 Explanation: type(x) returns the object's class. isinstance(x, int) is preferred for checks because it respects inheritance.

20What is the output of 10 % 3?

Answer: 1

💡 Explanation: The modulo operator % returns the remainder of a division. 10 divided by 3 is 3 with a remainder of 1.

21What is an f-string?

Answer: A formatted string literal, prefixed with f, that embeds expressions inside {}.

💡 Explanation: Introduced in Python 3.6, f"{name}" inserts the value of name directly into the string, which is fast and readable.

22What is the difference between append() and extend() on a list?

Answer: append() adds a single element; extend() adds each element of an iterable.

💡 Explanation: [1,2].append([3,4]) gives [1,2,[3,4]], while [1,2].extend([3,4]) gives [1,2,3,4].

23What does the "in" operator do?

Answer: Tests membership (whether a value exists in a sequence).

💡 Explanation: "a" in "cat" returns True. It works with strings, lists, tuples, sets, and dictionary keys.

24How do you reverse a string in Python?

Answer: Using slicing: s[::-1].

💡 Explanation: The slice [::-1] steps through the string backwards, producing a reversed copy.

25What does str.strip() do?

Answer: Removes leading and trailing whitespace (or specified characters).

💡 Explanation: " hi ".strip() returns "hi". Use lstrip() or rstrip() to trim only one side.

26How do you split a string into a list of words?

Answer: Using str.split().

💡 Explanation: "a b c".split() returns ["a", "b", "c"]. By default it splits on any run of whitespace.

27How do you join a list of strings into one string?

Answer: Using str.join(), e.g. ", ".join(list).

💡 Explanation: The separator string calls join on the iterable: ", ".join(["a","b"]) returns "a, b".

28What is the difference between str.find() and str.index()?

Answer: find() returns -1 if not found; index() raises a ValueError.

💡 Explanation: Both return the position of a substring, but they differ in how they handle a missing substring.

29What does the "r" prefix do in r"\n"?

Answer: Creates a raw string where backslashes are treated literally.

💡 Explanation: r"\n" is a two-character string (backslash + n), not a newline. Raw strings are common in regular expressions.

30How do you remove duplicates from a list?

Answer: Convert to a set and back: list(set(my_list)).

💡 Explanation: set() drops duplicates but loses order. Use dict.fromkeys() to remove duplicates while preserving order.

31What does list.pop() do without an argument?

Answer: Removes and returns the last element.

💡 Explanation: pop(i) removes the element at index i; pop() with no argument defaults to the last element.

32What is a dictionary comprehension?

Answer: A concise way to build a dict, e.g. {k: v for k, v in items}.

💡 Explanation: {x: x**2 for x in range(3)} produces {0: 0, 1: 1, 2: 4}.

33How do you safely get a dictionary value without risking a KeyError?

Answer: Use dict.get(key, default).

💡 Explanation: d.get("x", 0) returns 0 if "x" is missing, instead of raising a KeyError like d["x"] would.

34What does sorted() return compared to list.sort()?

Answer: sorted() returns a new list; list.sort() sorts in place and returns None.

💡 Explanation: Use sorted() when you must keep the original order intact, and .sort() when in-place reordering is fine.

35How do you merge two dictionaries in Python 3.9+?

Answer: Using the | operator: d1 | d2.

💡 Explanation: Python 3.9 added dict merging with |. Before that, {**d1, **d2} or d1.update(d2) were common.

36What is the difference between set.remove() and set.discard()?

Answer: remove() raises KeyError if the item is missing; discard() does not.

💡 Explanation: Both delete an element from a set, but discard() fails silently when the item is absent.

37What does enumerate() do?

Answer: Yields (index, value) pairs while iterating.

💡 Explanation: for i, v in enumerate(seq) gives both the index and the value on each iteration, avoiding manual counters.

38What does zip() do?

Answer: Combines multiple iterables element-wise into tuples.

💡 Explanation: zip([1,2], [3,4]) yields (1,3) and (2,4). It stops at the shortest iterable.

39How do you count occurrences of items in a list efficiently?

Answer: Using collections.Counter.

💡 Explanation: Counter(my_list) returns a dict-like object mapping each element to how many times it appears.

40What does the slice list[1:4] return?

Answer: Elements at indices 1, 2, and 3 (stop is exclusive).

💡 Explanation: Slicing is start-inclusive and stop-exclusive, so list[1:4] returns three elements.

41What is *args used for in a function definition?

Answer: To accept any number of positional arguments as a tuple.

💡 Explanation: def f(*args) collects extra positional arguments into a tuple named args.

42What is **kwargs used for?

Answer: To accept any number of keyword arguments as a dictionary.

💡 Explanation: def f(**kwargs) collects extra keyword arguments into a dict named kwargs.

43What is a lambda function?

Answer: A small anonymous function defined with the lambda keyword.

💡 Explanation: lambda x: x + 1 is a one-line function, often passed to map(), filter(), or sorted().

44What does the "global" keyword do?

Answer: Lets a function modify a variable in the global scope.

💡 Explanation: Without "global x", assigning to x inside a function creates a new local variable instead of changing the global one.

45Can a Python function return multiple values?

Answer: Yes, by returning a tuple.

💡 Explanation: return a, b returns a tuple that the caller can unpack: x, y = func().

46What does the "nonlocal" keyword do?

Answer: Lets a nested function modify a variable in the enclosing (non-global) scope.

💡 Explanation: nonlocal rebinds a variable from the outer function's scope rather than creating a new local one.

47What is the LEGB rule for name resolution?

Answer: Local, Enclosing, Global, Built-in.

💡 Explanation: Python resolves names in that order: local scope first, then enclosing functions, then module-global, then built-ins.

48What is recursion?

Answer: A function calling itself to solve a problem.

💡 Explanation: Recursion needs a base case to stop. Python's default recursion limit is around 1000 to avoid stack overflow.

49What does the "self" parameter refer to in a method?

Answer: The current instance of the class.

💡 Explanation: self is the conventional name for the instance automatically passed as the first argument to instance methods.

50What is inheritance in OOP?

Answer: A class deriving attributes and methods from a parent class.

💡 Explanation: class Dog(Animal) makes Dog inherit from Animal, reusing and extending its behaviour.

51What is method overriding?

Answer: Redefining a parent class method in a child class.

💡 Explanation: The child's version replaces the parent's when called on a child instance, enabling polymorphism.

52What is the difference between a classmethod and a staticmethod?

Answer: A classmethod receives the class (cls); a staticmethod receives neither self nor cls.

💡 Explanation: @classmethod suits factory methods; @staticmethod is a plain utility function grouped inside a class.

53What does the __str__ method do?

Answer: Defines the human-readable string representation of an object.

💡 Explanation: It is used by str() and print(). __repr__ instead provides an unambiguous, developer-facing representation.

54What does super() do?

Answer: Calls a method from the parent class.

💡 Explanation: super().__init__() invokes the parent's constructor, commonly used to initialise inherited attributes.

55What is the difference between a class variable and an instance variable?

Answer: A class variable is shared by all instances; an instance variable is unique to each object.

💡 Explanation: Class variables are defined at class level; instance variables are usually set on self inside __init__.

56What is polymorphism?

Answer: Different objects responding to the same method call in their own way.

💡 Explanation: Calling .area() on Circle and Square objects runs each class's own implementation of the method.

57What does a leading double underscore (__x) do to an attribute?

Answer: Triggers name mangling to make it harder to access from outside.

💡 Explanation: Python renames __x to _ClassName__x, providing a weak form of "private" attribute by convention.

58What is the main advantage of a generator over a list?

Answer: It produces items lazily, using far less memory.

💡 Explanation: Generators yield one item at a time instead of building the entire sequence in memory at once.

59What keyword turns a function into a generator?

Answer: yield

💡 Explanation: A function containing yield returns a generator object; execution pauses and resumes at each yield.

60How do you create a generator expression?

Answer: Use parentheses: (x for x in iterable).

💡 Explanation: Generator expressions look like comprehensions but use () and evaluate lazily instead of building a list.

61What does next() do with a generator?

Answer: Retrieves the next value, advancing the generator.

💡 Explanation: next(gen) resumes execution until the next yield, and raises StopIteration when the generator is exhausted.

62What is a decorator?

Answer: A function that wraps another function to extend its behaviour.

💡 Explanation: Decorators use the @ syntax: they take a function, add functionality, and return a new function.

63What is a closure?

Answer: A nested function that remembers variables from its enclosing scope.

💡 Explanation: The inner function retains access to the outer function's variables even after the outer function has returned.

64What does the @property decorator do?

Answer: Lets a method be accessed like an attribute.

💡 Explanation: @property turns a getter method into a read-only computed attribute accessed without parentheses.

65What does functools.wraps do inside a decorator?

Answer: Preserves the wrapped function's name and docstring.

💡 Explanation: Without @wraps, the decorated function loses its original __name__ and __doc__ metadata.

66Are functions first-class objects in Python?

Answer: Yes.

💡 Explanation: Functions can be assigned to variables, passed as arguments, and returned from other functions.

67Which block always runs whether or not an exception occurs?

Answer: The finally block.

💡 Explanation: finally is used for cleanup such as closing files or releasing locks, and runs regardless of exceptions.

68How do you handle a specific exception type?

Answer: Use try/except with that exception, e.g. except ValueError.

💡 Explanation: A bare except: catches everything and is discouraged because it can hide bugs.

69What does the "raise" keyword do?

Answer: Manually triggers (raises) an exception.

💡 Explanation: raise ValueError("bad input") stops normal flow and signals an error to be handled by a try/except.

70What does the "else" clause of a try statement do?

Answer: Runs only if no exception was raised in the try block.

💡 Explanation: It keeps success-only code separate from the error-handling code in except.

71What is the base class of most built-in exceptions?

Answer: Exception (which inherits from BaseException).

💡 Explanation: Custom exceptions should subclass Exception, not BaseException, to behave like standard errors.

72How do you import a specific function from a module?

Answer: Using "from module import function".

💡 Explanation: from math import sqrt lets you call sqrt() directly without the math. prefix.

73What does "if __name__ == '__main__':" do?

Answer: Runs code only when the file is executed directly, not when imported.

💡 Explanation: This guard prevents a module's script code from running when the module is imported elsewhere.

74Which module provides random number functions?

Answer: The random module.

💡 Explanation: random.randint(), random.choice(), and random.shuffle() are commonly used functions from it.

75Which module is used for regular expressions?

Answer: The re module.

💡 Explanation: re.match(), re.search(), and re.findall() provide pattern-matching functionality.

76What does pip do?

Answer: Installs and manages third-party Python packages.

💡 Explanation: pip install <package> downloads packages from PyPI, the Python Package Index.

77What is a virtual environment used for?

Answer: To isolate a project's dependencies from other projects.

💡 Explanation: Tools like venv create isolated environments so package versions do not conflict across projects.

78What is the output of: print(2 ** 3 ** 2)?

Answer: 512

💡 Explanation: The ** operator is right-associative, so it evaluates as 2 ** (3 ** 2) = 2 ** 9 = 512.

79What is the output of: print(bool(0), bool([]), bool("0"))?

Answer: False False True

💡 Explanation: 0 and [] are falsy, but the non-empty string "0" is truthy — any non-empty string evaluates to True.

80What is the output of: print([1, 2, 3][-1])?

Answer: 3

💡 Explanation: Negative indexing counts from the end, so index -1 is the last element.

81What is the output of: print("5" + "5")?

Answer: '55'

💡 Explanation: The + operator concatenates strings. Numeric addition would need int("5") + int("5") = 10.

82What is the output of: print(list(range(1, 10, 2)))?

Answer: [1, 3, 5, 7, 9]

💡 Explanation: range(start, stop, step) with step 2 yields every second number from 1 up to (not including) 10.

83What is the output of: print(3 == 3.0)?

Answer: True

💡 Explanation: Python compares numeric values across types, so the integer 3 equals the float 3.0.

84What is the output of: print("abc"[::2])?

Answer: 'ac'

💡 Explanation: The slice [::2] takes every second character starting at index 0.

85What is the output of: x = [1,2,3]; y = x; y.append(4); print(x)?

Answer: [1, 2, 3, 4]

💡 Explanation: y = x makes both names reference the same list object, so appending through y also changes x.

86What is the output of: print(type(5 / 2))?

Answer: <class 'float'>

💡 Explanation: The / operator always returns a float in Python 3, even when the operands divide evenly.

87What is the output of: print("Python".lower().upper())?

Answer: 'PYTHON'

💡 Explanation: Method chaining: .lower() returns "python", then .upper() returns "PYTHON".

88What is the output of: print(len({1, 1, 2, 3, 3}))?

Answer: 3

💡 Explanation: A set literal removes duplicates, leaving {1, 2, 3}, which has length 3.

89What is the output of: print(1 == True)?

Answer: True

💡 Explanation: bool is a subclass of int in Python, where True equals 1 and False equals 0.

90What is the difference between "==" for lists and "is" for lists?

Answer: "==" checks equal contents; "is" checks they are the same object.

💡 Explanation: [1,2] == [1,2] is True, but [1,2] is [1,2] is False because they are two distinct list objects.

91What does the * operator do in a call like func(*my_list)?

Answer: Unpacks the iterable into separate positional arguments.

💡 Explanation: func(*[1,2,3]) is equivalent to func(1, 2, 3). Similarly ** unpacks a dict into keyword arguments.

92What does a slice assignment like list[:] = [] do?

Answer: Clears the list in place while keeping the same object.

💡 Explanation: It empties the existing list object, so other references to that list also see it become empty.

93What is the difference between deepcopy and assignment for nested lists?

Answer: Assignment shares the same object; deepcopy creates fully independent nested copies.

💡 Explanation: copy.deepcopy() recursively copies nested objects so changes to the copy do not affect the original.

94What does the walrus operator := do?

Answer: Assigns a value as part of an expression.

💡 Explanation: Added in Python 3.8, it lets you assign and use a value at once, e.g. if (n := len(data)) > 10:.

95What is the output of: print("hello".replace("l", "L"))?

Answer: 'heLLo'

💡 Explanation: replace() returns a new string with all occurrences of the substring replaced (both l characters here).

96What does the map() function do?

Answer: Applies a function to every item of an iterable, returning a map object.

💡 Explanation: list(map(str, [1,2,3])) returns ["1","2","3"]. Wrap it in list() to see the results.

97What does the filter() function do?

Answer: Keeps only items for which a function returns True.

💡 Explanation: list(filter(lambda x: x > 0, [-1, 2, -3, 4])) returns [2, 4].

98What does the "pass" statement do?

Answer: Nothing — it is a placeholder where a statement is syntactically required.

💡 Explanation: pass is used in empty function bodies, loops, or class definitions you intend to fill in later.

99What is the output of: print(bool(None))?

Answer: False

💡 Explanation: None is falsy, so bool(None) evaluates to False.

100What does dict.items() return?

Answer: A view of (key, value) pairs.

💡 Explanation: for k, v in d.items() iterates over both keys and values together. keys() and values() return the parts separately.

• Write readable PEP 8 compliant code - Name variables clearly and use space formatting.
• Understand complexity overheads - Know time complexities (O-notation) for dictionary lookups, list inserts, and sorting.
• Master built-in libraries - Be proficient with itertools, collections, and copy modules.
• Focus on error exceptions - Handle errors gracefully with try-except-finally context guards.