Advanced Concepts — Python Questions with Answers

Q5. medium

What is the walrus operator := used for (Python 3.8+)?

while (line := input()) != "quit":
    print(line)

# instead of:
# line = input()
# while line != 'quit': ... line = input()

1. A Assign a value AND use it in the same expression
2. B Compare two values
3. C Multiply and assign
4. D Unpack a tuple

Q6. medium

What does *rest capture here? a, *rest = [1, 2, 3, 4]

a, *rest = [1, 2, 3, 4]
print(a, rest)          # 1 [2, 3, 4]
first, *mid, last = [1, 2, 3, 4]
print(mid)               # [2, 3]

1. A a = 1 and rest = [2, 3, 4] - starred unpacking grabs the remaining items as a list
2. B a = [1, 2, 3, 4], rest = []
3. C a = 1, rest = 2
4. D Error

Q8. medium

What are type hints, and are they enforced at runtime? def f(x: int) -> str:

def greet(name: str) -> str:
    return "Hi " + name
greet(123)   # runs (then crashes on +), hints not enforced

1. A Annotations documenting expected types; NOT enforced - tools like mypy check them, Python ignores them
2. B Strict runtime type checks
3. C Comments only
4. D Required in Python 3

Q13. medium

What is an f-string's = debug feature (Python 3.8+)? print(f"{x=}")

x = 5
print(f"{x=}")          # x=5
print(f"{x * 2=}")      # x * 2=10

1. A Prints both the expression and its value: x=5
2. B Compares x to 5
3. C Assigns 5 to x
4. D Prints just the value

Q16. medium

What does zip(*matrix) do to matrix = [[1, 2], [3, 4]]?

matrix = [[1, 2], [3, 4]]
print(list(zip(*matrix)))   # [(1, 3), (2, 4)]

1. A Transposes it: [(1, 3), (2, 4)] - rows become columns
2. B Flattens it
3. C Reverses it
4. D Sums the rows

Q19. medium

What does enumerate(items, start=1) change?

for i, name in enumerate(["a", "b"], start=1):
    print(i, name)   # 1 a / 2 b

1. A Numbering begins at 1 instead of 0
2. B It starts from the second item
3. C It reverses the items
4. D Nothing

Q22. medium

What does the ternary/conditional expression evaluate to? x = a if condition else b

status = "adult" if age >= 18 else "minor"

1. A a when condition is True, otherwise b
2. B Always a
3. C A tuple (a, b)
4. D b when condition is True

Q25. medium

What does the else clause of a for loop do? for x in items: if x == target: break else: print("not found")

1. A Runs only if the loop finished WITHOUT hitting break
2. B Runs after every iteration
3. C Runs only when break happens
4. D Is a syntax error

Q27. medium

What does any() with a generator do? any(x > 100 for x in nums)

has_big = any(x > 100 for x in nums)
all_positive = all(x > 0 for x in nums)

1. A Returns True if at least one item satisfies the condition, stopping early on the first True
2. B Returns all matching items
3. C Counts the matches
4. D Returns the largest item

Q29. medium

What does sorted(data, key=lambda x: x[1], reverse=True) do?

pairs = [("a", 3), ("b", 1)]
print(sorted(pairs, key=lambda x: x[1]))   # [('b', 1), ('a', 3)]

1. A Sorts data by each item's second element, in descending order
2. B Sorts alphabetically
3. C Reverses without sorting
4. D Sorts by the first element ascending

Q1. hard

What is the GIL (Global Interpreter Lock)?

1. A A lock that lets only ONE thread run Python bytecode at a time in CPython
2. B A security feature for imports
3. C A garbage collector
4. D A way to lock files

Q2. hard

For CPU-heavy work needing real parallelism, which should you use?

1. A multiprocessing - separate processes each with their own interpreter, bypassing the GIL
2. B threading - always faster
3. C A bigger for loop
4. D asyncio

Q3. hard

What is the difference between a shallow copy and a deep copy?

import copy
a = [[1, 2], [3, 4]]
b = a.copy()          # shallow
b[0][0] = 99
print(a)               # [[99, 2], [3, 4]] - inner shared!
c = copy.deepcopy(a)   # fully independent

1. A Shallow copies the outer object but shares nested objects; deep copies everything recursively
2. B They are identical
3. C Deep copy is faster
4. D Shallow copy only works on strings

Q4. hard

What is the output? a = [[0, 0], [0, 0]] b = a[:] b[0][1] = 9 print(a[0][1])

1. A 9 - the slice is a shallow copy, so the inner lists are shared
2. B 0 - b is fully independent
3. C None
4. D Error

Q7. hard

What does the ** operator do here? combined = {**dict1, **dict2}

a = {"x": 1, "y": 2}
b = {"y": 99, "z": 3}
print({**a, **b})   # {'x': 1, 'y': 99, 'z': 3}

1. A Merges the two dicts into a new one; dict2's values win on key clashes
2. B Multiplies the dicts
3. C Raises dict1 to the power dict2
4. D Compares the dicts

Q9. hard

What does this type hint mean? from typing import Optional def find(id: int) -> Optional[str]:

def find_user(id: int) -> Optional[str]:
    return names.get(id)   # str or None

1. A The function returns a str OR None
2. B The argument is optional
3. C The function might not exist
4. D It returns an optional number

Q10. hard

What is a context manager?

from contextlib import contextmanager
@contextmanager
def tag(name):
    print(f"<{name}>")
    yield
    print(f"</{name}>")
with tag("b"):
    print("hi")

1. A An object usable with 'with' that runs setup on entry and cleanup on exit (via __enter__/__exit__)
2. B A manager class for variables
3. C A type of decorator
4. D A threading tool

Q11. hard

What is monkey patching?

import time
time.sleep = lambda s: None   # patch away real sleeping in tests

1. A Modifying or replacing a class/module's attributes at RUNTIME
2. B Fixing bugs with a debugger
3. C A testing framework
4. D Writing messy code

Q12. hard

What does __slots__ do in a class?

class Point:
    __slots__ = ('x', 'y')
    def __init__(self, x, y):
        self.x, self.y = x, y
p = Point(1, 2)
# p.z = 3   # AttributeError - not in __slots__

1. A Restricts instances to a fixed set of attributes, saving memory by removing the per-instance __dict__
2. B Creates database slots
3. C Adds time slots
4. D Makes the class abstract

Q14. hard

What does @dataclass reduce boilerplate for?

from dataclasses import dataclass
@dataclass
class Point:
    x: int
    y: int
print(Point(1, 2))   # Point(x=1, y=2)

1. A Auto-generating __init__, __repr__, and __eq__ from declared fields
2. B Database connections
3. C File handling
4. D Threading

Q15. hard

What is the output? from collections import defaultdict d = defaultdict(list) d["a"].append(1) print(d["a"])

from collections import defaultdict
groups = defaultdict(list)
for name in ["ana", "amy", "bob"]:
    groups[name[0]].append(name)   # group by first letter

1. A [1] - defaultdict auto-creates an empty list for a missing key
2. B KeyError
3. C None
4. D []

Q17. hard

What is the difference between is and == (recap for advanced code)?

a = [1, 2]; b = [1, 2]
print(a == b)   # True - equal values
print(a is b)   # False - different objects

1. A == compares values; is checks whether two names point to the exact same object
2. B They are the same
3. C is compares values
4. D == only works on numbers

Q18. hard

Why can small ints behave oddly with is? a = 256; b = 256; print(a is b) # True a = 257; b = 257; print(a is b) # often False

1. A CPython caches small integers (-5 to 256), so identical small ints share one object; larger ones may not
2. B It's a bug
3. C 256 is special in binary
4. D is never works on numbers

Q20. hard

What is a generator's role in the memory-efficient processing of big data?

lines = (l.strip() for l in open("huge.log"))
errors = (l for l in lines if "ERROR" in l)
for e in errors: ...   # constant memory

1. A It yields items lazily, so pipelines process huge datasets without loading everything into memory
2. B It compresses the data
3. C It stores data on disk
4. D It runs on the GPU

Q21. hard

What does functools.partial do? from functools import partial square = partial(pow, exp=2)

from functools import partial
cube = partial(pow, exp=3)
print(cube(2))   # 8

1. A Creates a new function with some arguments pre-filled
2. B Splits a function in half
3. C Runs a function partially then pauses
4. D Caches results

Q23. hard

What is the output? print(list(zip([1, 2, 3], ["a", "b"])))

from itertools import zip_longest
print(list(zip_longest([1,2,3], ["a","b"], fillvalue="?")))
# [(1,'a'), (2,'b'), (3,'?')]

1. A [(1, 'a'), (2, 'b')] - zip stops at the SHORTER iterable
2. B [(1, 'a'), (2, 'b'), (3, None)]
3. C Error - lengths differ
4. D [(1, 2, 3), ('a', 'b')]

Q24. hard

What are *args and **kwargs at a CALL site (unpacking)? f(*my_list, **my_dict)

def add(a, b, c): return a + b + c
nums = [1, 2, 3]
print(add(*nums))   # 6

1. A * spreads a list into positional arguments; ** spreads a dict into keyword arguments
2. B They multiply the arguments
3. C They create new lists
4. D They are only valid in definitions

Q26. hard

What is the output? x = 10 def f(): print(x) x = 20 f()

1. A UnboundLocalError - assigning x anywhere makes it local for the whole function
2. B 10
3. C 20
4. D None

Q28. hard

What is a metaclass, in one line?

class Meta(type): ...
class MyClass(metaclass=Meta): ...

1. A The 'class of a class' - it controls how classes themselves are created (type is the default metaclass)
2. B A class with metadata
3. C A very large class
4. D An abstract base class

Q30. hard

What is the output? print([1, 2, 3] * 2) print((1, 2) + (3,))

1. A [1, 2, 3, 1, 2, 3] and (1, 2, 3)
2. B [2, 4, 6] and (4, 5)
3. C Error
4. D [1, 2, 3, 2] and (1, 5)