Question 1

Which Python data types are mutable and which are immutable?

Accepted Answer

Mutable types (list, dict, set) can be changed in place; immutable types (int, float, str, tuple, frozenset) cannot. This matters for test data shared across tests and for dict keys.

Question 2

Difference between list, tuple, set and dict, with automation use cases?

Accepted Answer

A list is an ordered mutable sequence, a tuple is an ordered immutable sequence, a set holds unique unordered items, and a dict maps keys to values. In tests you use lists for element collections, tuples for locators and parametrize rows, sets for uniqueness checks and dicts for payloads.

Question 3

What are list and dict comprehensions?

Accepted Answer

Comprehensions build lists, dicts or sets in a single readable expression with optional filtering. They're commonly used to extract texts from elements or transform API data.

Question 4

What are *args and **kwargs?

Accepted Answer

*args collects extra positional arguments into a tuple and **kwargs collects extra keyword arguments into a dict. They let wrapper utilities pass arguments through to underlying functions.

Question 5

How does exception handling work in Python?

Accepted Answer

Use try/except to catch specific exceptions, else for code that runs when nothing failed, and finally for cleanup that always runs. Raise custom exceptions for clear framework errors.

Question 6

What is a virtual environment and why use one for automation projects?

Accepted Answer

A virtual environment is an isolated Python installation with its own packages, so each project pins its own versions of selenium, pytest and others. It keeps local runs and CI reproducible.

Question 7

How does pytest discover tests and what are its advantages?

Accepted Answer

pytest discovers files named test_*.py or *_test.py, functions prefixed test_ and classes prefixed Test without __init__. It uses plain assert with rich failure output, fixtures and a large plugin ecosystem.

Question 8

Explain pytest fixtures and scopes.

Accepted Answer

Fixtures provide setup and teardown via dependency injection: a test lists the fixture name as a parameter. Code before yield is setup, after yield is teardown, and scope controls lifetime (function, class, module, package, session).

Question 9

What is conftest.py?

Accepted Answer

conftest.py is a local plugin file where you define fixtures and hooks that are automatically available to all tests in that directory and below, without imports.

Question 10

How do you do data-driven testing in pytest?

Accepted Answer

Use @pytest.mark.parametrize to run one test with multiple input sets; each set becomes a separate test case. Data can also come from CSV/JSON files or parametrized fixtures.

Question 11

What is a decorator? Write one useful for tests.

Accepted Answer

A decorator is a function that takes a function and returns a wrapped version, adding behavior without changing its code. In automation it's used for retries, timing, logging and pytest markers/fixtures themselves.

Question 12

What are generators and the yield keyword?

Accepted Answer

A generator is a function using yield to produce values lazily one at a time, keeping state between calls. It saves memory for large datasets and powers pytest's yield fixtures.

Question 13

How do you test REST APIs with the requests library?

Accepted Answer

Send HTTP calls with requests (get, post, put, delete), then assert on status_code, headers and response.json(). Use a Session for shared headers/auth and connection reuse.

Question 14

How do you handle waits in Selenium with Python?

Accepted Answer

Use explicit waits with WebDriverWait and expected_conditions to wait for a specific state. Avoid time.sleep and avoid mixing implicit and explicit waits.

Question 15

How does Playwright for Python differ from Selenium?

Accepted Answer

Playwright drives Chromium, Firefox and WebKit over a persistent connection, with built-in auto-waiting, web-first assertions, network interception and tracing. pytest-playwright provides a ready page fixture.

Question 16

Reverse a string and reverse each word in a sentence.

Accepted Answer

Slicing with s[::-1] reverses a string in O(n). For words, split, reverse each word or the list, and join back.

Question 17

Find duplicates in a list.

Accepted Answer

Track seen items in a set and collect any item seen again, which is O(n). collections.Counter gives counts in one line.

Question 18

Check whether a string is a palindrome in Python, ignoring case and punctuation.

Accepted Answer

Normalize the string (lowercase, keep alphanumerics) and compare it with its reverse. A two-pointer loop avoids creating a reversed copy.

Question 19

Count character or word frequency and find the first non-repeating character.

Accepted Answer

Use a dict with get(c, 0) + 1 or collections.Counter to count occurrences. Since dicts keep insertion order, the first key with count 1 is the first non-repeating character.

Question 20

How do you structure a Page Object Model framework in Python?

Accepted Answer

Create a BasePage with shared wait/click helpers, page classes holding locators as class-level tuples and action methods, and pytest fixtures in conftest.py that provide the driver and pages. Tests stay short and read like user flows.

Question 21

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

Accepted Answer

== compares values by calling __eq__, while is checks whether two names point to the same object in memory. Use is only for singletons like None, True and False.

Question 22

How do string slicing and common string methods work in Python?

Accepted Answer

Slicing uses s[start:stop:step], where stop is exclusive and negative indexes count from the end. Common methods include strip, split, join, replace, lower, startswith and f-strings for formatting.

Question 23

What are lambda, map, filter and sorted with a key?

Accepted Answer

A lambda is a small anonymous single-expression function. map applies a function to every item, filter keeps items where a function returns true, and sorted(key=...) orders items by a computed value.

Question 24

How do you read and write files in Python, including CSV and JSON test data?

Accepted Answer

Use open() inside a with statement so the file closes automatically, even on errors. The json and csv modules parse structured test data into dicts and lists.

Question 25

Explain classes, __init__ and self in Python.

Accepted Answer

A class is a blueprint for objects; __init__ initializes a new instance and self is the reference to that instance, passed automatically as the first argument of instance methods. Attributes set on self belong to each object.

Question 26

What does if __name__ == "__main__" do, and how do modules and packages work?

Accepted Answer

Every module has a __name__; it equals "__main__" only when the file is run directly, so the guarded block won't execute on import. A package is a directory of modules, traditionally marked with __init__.py.

Question 27

How do range, enumerate and zip help when looping in Python?

Accepted Answer

range generates integer sequences lazily, enumerate yields index-value pairs so you don't track counters manually, and zip walks several iterables in parallel, stopping at the shortest.

Question 28

Write FizzBuzz in Python.

Accepted Answer

Loop from 1 to n; print FizzBuzz for multiples of both 3 and 5, Fizz for 3, Buzz for 5, otherwise the number. Building the string by concatenation avoids a separate 15 check.

Question 29

Generate the Fibonacci sequence in Python using a generator.

Accepted Answer

Keep two variables a and b, yield a, then update with tuple unpacking a, b = b, a + b. A generator produces terms lazily, and recursion with lru_cache is the memoized alternative.

Question 30

Check if a number is prime and list primes in a range in Python.

Accepted Answer

Numbers below 2 are not prime; otherwise test divisors from 2 up to the integer square root. If none divides evenly the number is prime.

Question 31

Count vowels and consonants in a string in Python.

Accepted Answer

Lowercase the string, then for each alphabetic character check membership in a vowel set. Set membership is O(1), and str.isalpha() skips digits, spaces and punctuation.

Question 32

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

Accepted Answer

A shallow copy creates a new outer container but shares the nested objects, while a deep copy recursively copies everything. Mutating a nested dict in a shallow copy also changes the original.

Question 33

How do inheritance, super() and MRO work in Python?

Accepted Answer

A subclass inherits attributes and methods and can override them; super() calls the next class in the method resolution order. Python supports multiple inheritance and uses C3 linearization to decide the MRO.

Question 34

What are dunder (magic) methods? Give useful examples.

Accepted Answer

Dunder methods like __init__, __str__, __repr__, __eq__, __len__ and __iter__ let your classes integrate with Python syntax and built-ins. For example, __eq__ makes == compare test objects meaningfully.

Question 35

What is the difference between @staticmethod, @classmethod and an instance method?

Accepted Answer

An instance method receives self and works with object state. A classmethod receives cls and is commonly used for alternative constructors, while a staticmethod receives neither and is just a function namespaced in the class.

Question 36

What is the GIL, and when do you use threading, multiprocessing or asyncio?

Accepted Answer

In CPython the Global Interpreter Lock lets only one thread execute Python bytecode at a time, so threads don't speed up CPU-bound code. Threads and asyncio suit I/O-bound work like HTTP calls, while multiprocessing gives true parallelism for CPU-bound tasks.

Question 37

How does unittest work and how does it compare with pytest?

Accepted Answer

unittest is the built-in xUnit-style framework: tests are methods starting with test inside a unittest.TestCase subclass, with setUp/tearDown hooks and self.assert* methods. pytest can run unittest tests too, but offers plain assert, fixtures and plugins with less boilerplate.

Question 38

How do you use pytest markers, skip and xfail?

Accepted Answer

Markers tag tests so you can select them with -m, for example smoke or regression. skip/skipif skips a test unconditionally or on a condition, and xfail marks an expected failure such as a known bug.

Question 39

How do you run pytest in parallel and configure it with pytest.ini?

Accepted Answer

Install pytest-xdist and run pytest -n auto to spread tests across worker processes. pytest.ini (or pyproject.toml) holds defaults like addopts, testpaths, markers and timeouts.

Question 40

How do you write a custom context manager?

Accepted Answer

Implement __enter__ and __exit__ on a class, or decorate a generator with contextlib.contextmanager and yield once. Code after yield runs as cleanup, even if the block raises.

Question 41

Check whether two words are anagrams using Counter.

Accepted Answer

Normalize both strings and compare their character counts with collections.Counter, which is O(n). sorted(a) == sorted(b) also works in O(n log n).

Question 42

Find the second largest distinct number in a list without sorting.

Accepted Answer

Track the largest and second largest in one pass, updating second whenever a value beats it but differs from the largest. Return None if no second distinct value exists.

Question 43

Find the missing number in a list of 1 to n in Python.

Accepted Answer

The sum of 1 to n is n * (n + 1) // 2; subtract sum(nums) to get the missing value. For several missing numbers, use set difference against range(1, n + 1).

Question 44

How do you sort a dictionary by value and merge two dictionaries?

Accepted Answer

Use sorted(d.items(), key=lambda kv: kv[1]) and rebuild a dict, since dicts keep insertion order. Merge with the | operator (Python 3.9+) or {**a, **b}; keys on the right win.

Question 45

How do async and await work in Python with asyncio?

Accepted Answer

async def defines a coroutine, and await pauses it until another awaitable finishes, letting the event loop run other tasks meanwhile. asyncio.gather runs many I/O-bound coroutines concurrently in a single thread.

Question 46

How do type hints and dataclasses improve a Python test framework?

Accepted Answer

Type hints document expected types and let tools like mypy and IDEs catch mistakes before runtime, though Python doesn't enforce them. @dataclass generates __init__, __repr__ and __eq__ for data-holding classes like test users or API models.

Question 47

How does Python manage memory and garbage collection?

Accepted Answer

CPython frees most objects immediately via reference counting when their count drops to zero. A cyclic garbage collector periodically finds and frees reference cycles that reference counting alone can't reclaim.

Question 48

Which features from Python 3.8 to 3.12+ are useful in automation code?

Accepted Answer

Useful additions include the walrus operator (3.8), dict union | (3.9), structural pattern matching with match/case and X | Y type unions (3.10), exception groups and tomllib (3.11), and simpler f-string and generic syntax (3.12).

Question 49

Implement a sorting algorithm in Python without using sort() or sorted().

Accepted Answer

Bubble sort compares adjacent pairs and swaps them when out of order, pushing the largest to the end each pass; stop early when a pass makes no swaps. Insertion sort is a similar O(n^2) option that's efficient on nearly sorted data.

Question 50

How do you use pytest hooks to capture screenshots on failure?

Accepted Answer

Implement the pytest_runtest_makereport hook in conftest.py as a hookwrapper, read the report after the call phase, and when it failed grab the driver or page from the test's fixtures to save a screenshot.

Interview Questions

01Which Python data types are mutable and which are immutable?BeginnerCore Python

02Difference between list, tuple, set and dict, with automation use cases?BeginnerCore Python

03What are list and dict comprehensions?BeginnerCore Python

04What are *args and **kwargs?BeginnerCore Python

05How does exception handling work in Python?BeginnerCore Python

06What is a virtual environment and why use one for automation projects?BeginnerTooling & Libraries

07How does pytest discover tests and what are its advantages?Beginnerpytest

08Explain pytest fixtures and scopes.Intermediatepytest

09What is conftest.py?Intermediatepytest

10How do you do data-driven testing in pytest?Intermediatepytest

11What is a decorator? Write one useful for tests.IntermediateAdvanced Python

12What are generators and the yield keyword?IntermediateAdvanced Python

13How do you test REST APIs with the requests library?IntermediateTooling & Libraries

14How do you handle waits in Selenium with Python?IntermediateTooling & Libraries

15How does Playwright for Python differ from Selenium?AdvancedTooling & Libraries