Python MCQ Questions

map() function applies function to all items in iterable. Syntax: map(function, iterable). Returns map object (iterator). Example: list(map(lambda x: x*2, [1,2,3])) returns [2,4,6]. Applies transformation to each element. Functional programming construct. Common with lambda functions.

Use sys.path to see module search paths. List of directory strings. Modify to add locations: sys.path.append('/my/path'). First directory is script location. PYTHONPATH adds to path. Module import path management.

re.match() checks if pattern matches at string beginning. re.search() searches entire string for first match anywhere. match() anchored to start, search() finds anywhere. Example: re.match(r'\d+', 'abc123') returns None, re.search(r'\d+', 'abc123') finds '123'. Use match for start validation, search for finding.

Use datetime.timedelta for time duration. Example: delta = timedelta(days=7, hours=3). Arithmetic: dt + delta. Supports days, seconds, microseconds, milliseconds, minutes, hours, weeks. Duration representation.

Index of first item in Python tuple or list is 0 (zero-based indexing). First element accessed as my_list[0] or my_tuple[0]. Last element at index -1 (negative indexing from end). Zero-based indexing standard in Python and most programming languages. Understanding indexing essential for sequence access.

Future statement imports features from future Python versions. Syntax: from __future__ import feature. Example: from __future__ import division (Python 3 division in Python 2). Must be at file top (after docstring/comments). Enables forward compatibility. Prepares code for future Python versions.

Use complex(real, imag) for complex numbers. Example: complex(2, 3) creates 2+3j. complex('2+3j') from string. Supports math operations. real and imag attributes. abs() for magnitude. Complex number creation.

Text mode interprets data as strings, handles encoding (UTF-8 default), converts line endings. Binary mode treats data as bytes, no encoding, no line ending conversion. Text: open('file', 'r'), Binary: open('file', 'rb'). Use binary for images, executables. Text for text files. Mode affects read/write behavior.

Use contextlib.contextmanager for generator-based context managers. Example: @contextmanager def resource(): setup; yield obj; cleanup. Simpler than class. Resource management decorator.

Use contextlib.suppress(*exceptions) to ignore exceptions. Example: with suppress(FileNotFoundError): os.remove('file'). Cleaner than try-except pass. Exception suppression context.

String is sequence of characters. Immutable, ordered, iterable. Created with quotes: 'text', "text", '''text'''. Unicode in Python 3, bytes vs str distinction. Support slicing, concatenation, methods (upper, split, replace). Fundamental data type for text. Can be empty: ''. Indexed access: s[0].

Delegation is design pattern where object passes operation to another object (delegate). Instead of inheriting, contains delegate instance. Composition over inheritance. Example: class A: def method(self): self.delegate.method(). Enables code reuse, flexibility. Common in wrapper/proxy patterns. Favors has-a over is-a relationships.

Result: '%g' % 74 returns '74' (string), '7' is string '7'. %g formats number removing trailing zeros, scientific notation for large numbers. 74 becomes '74'. Expression ('%g' % 74, '7') creates tuple ('74', '7'). Result: tuple of two strings. %g general format.

pass statement is null operation - does nothing. Syntax placeholder when statement required but no action needed. Example: def func(): pass creates empty function. Used in: empty function/class definitions, if/else blocks, exception handlers. Pass allows syntactically correct code while developing. Actual implementation added later.

Assertion syntax: assert condition or assert condition, message. Example: assert x > 0, 'x must be positive'. Raises AssertionError if condition false. Optional message provides context. Used for debugging, testing invariants. Disabled with -O optimization flag. Not for error handling.

Argument order: positional, *args, keyword, **kwargs. Example: def func(a, b, *args, c=1, **kwargs). Positional first, varargs middle, keyword last. Python 3 keyword-only: after *args or standalone *. Order matters for function definition. Standard parameter ordering convention.

Use collections.OrderedDict to maintain insertion order. Python 3.7+ regular dicts ordered. OrderedDict still useful for explicit guarantee. move_to_end() method. Ordered dictionary.

Correct syntax: except ExceptionType as variable: or except (ExceptionType1, ExceptionType2) as e:. Example: except ValueError as e: print(e). 'as' keyword binds exception to variable. Python 3 uses 'as', Python 2 allowed 'as' or comma. Modern syntax uses 'as'.

Use isinstance(obj, type) for type checking. Returns boolean. Example: isinstance(5, int). Handles inheritance: isinstance(obj, ParentClass) returns True for subclasses. Multiple types: isinstance(x, (int, float)). Better than type() as respects inheritance. Standard type checking method.

Package is collection of modules organized in directory with __init__.py file. Directory structure for organizing related modules. Example: mypackage/ contains __init__.py and module files. Import: from mypackage import module. Packages enable hierarchical namespace, modular code organization. Can be nested for sub-packages.

Use collections.defaultdict for automatic defaults. Example: dd = defaultdict(list); dd['key'].append(value). No KeyError on missing keys. Factory function provides default. Convenient initialization.

htmllib is deprecated Python 2 module for parsing HTML. Replaced by html.parser in Python 3. Provided HTMLParser class for simple HTML processing. Modern alternatives: BeautifulSoup, lxml, html.parser. htmllib removed in Python 3. Legacy module for HTML parsing.

Statement 1: True. Assignment binds name in current scope unless declared global. Statement 2: True. global keyword binds to module level. Both statements correct. Scope rules for assignments. global declaration overrides local binding. Without global, assignments create local variables. Both statements accurately describe scope binding.

Use file.readline() to read next line up to \n. Returns string including newline character. file.read() reads entire file. file.readlines() returns list of all lines. readline() reads single line, advances file pointer. Empty string '' when end reached. Text file must be opened first.

Value of m is map object (iterator) containing [False, True, False, True, False, True, False, True, False]. map() applies lambda to each element. lambda x: x%2==0 checks if even. Convert: list(m). Python 3 map returns iterator not list. Pattern: even/odd booleans for 1-9.

Persistent dictionary is database-backed dictionary (dbm module). Key-value storage persisting across program runs. Interface like dict, data stored on disk. Example: import dbm; db=dbm.open('file','c'); db['key']='value'; db.close(). Simple database for key-value data. Alternative to pickle for simple storage.

__doc__ is docstring attribute containing function/class/module documentation. First string literal in definition. Accessed: function.__doc__. Example: def foo(): '''Docstring''' creates foo.__doc__='Docstring'. help() uses __doc__. Documents code purpose, usage. Convention for documentation.

Output: foo prints: 1 (newline) (2,3,4,5) (tuple). bar prints: 1 (newline) {'a':2,'b':3} (dict). *param2 captures extra positional as tuple. **param2 captures keyword args as dict. foo(1,2,3,4,5): param1=1, param2=(2,3,4,5). bar(1,a=2,b=3): param1=1, param2={'a':2,'b':3}. Demonstrates *args and **kwargs.

Extended unpacking: first, *middle, last = [1,2,3,4,5]. *variable captures remaining items. Example: head, *tail = mylist. Can appear once in assignment. Python 3 feature. Flexible sequence unpacking. Variable-length capture.

Use collections.ChainMap for combined dict views. Example: ChainMap(dict1, dict2). Searches dicts in order. Updates affect first dict only. Nested scope simulation. Multiple context management. Combined dictionary view.

Value of x is 10. [int(x) for x in '1'*10] creates [1,1,1,1,1,1,1,1,1,1]. reduce(lambda x,y: x+y, [1]*10) sums: 1+1+1+1+1+1+1+1+1+1=10. reduce() accumulates sum. '1'*10 = '1111111111', converted to list of ints, summed.

Default arguments evaluated once at definition. Mutable defaults shared across calls. Example: def func(lst=[]): lst.append(1) shares same list. Use None: def func(lst=None): lst = lst or []. Avoid mutable defaults (list, dict). Common pitfall. Use None then create inside function.

Use random.randint(a, b) for random integer [a, b] inclusive. Example: dice = random.randint(1, 6). Both endpoints included. random.randrange(a, b) excludes b. Integer random generation.

Output: [1], [1,2], [1,2,3]. Default mutable argument L=[] shared across calls. First f(1): L=[], append 1, return [1]. Second f(2): same L=[1], append 2, return [1,2]. Third f(3): same L=[1,2], append 3, return [1,2,3]. Mutable default pitfall. Use L=None, then L=L or [] inside function.

List comprehensions return list immediately, stored in memory. Generator expressions return generator (iterator), values produced on-demand (lazy evaluation). Syntax: [x for x in range(10)] vs (x for x in range(10)). Generators more memory-efficient for large sequences. Comprehensions faster for small data. Use generators for large/infinite sequences.

Use secrets module for cryptographic randomness. secrets.token_bytes(n) for random bytes. secrets.token_hex(n) for hex string. More secure than random. Password/token generation.

Output: 'AJon'. rjust(4, 'A') right-justifies in 4 characters, padding with 'A'. 'Jon' is 3 characters, needs 1 padding. Result: 'AJon'. rjust() pads on left. Width includes original string. Returns new string, original unchanged. Right-justified with custom fill character.

Value of c is 4. Expression: (a == 'text') is False, False and a is False (short-circuit), False or b returns b which is 4. Short-circuit: and stops at False, or continues to b. Result: 4. Logical operators with precedence.

Results: eval('7') returns integer 7, string.atoi('4') returns integer 4 (deprecated), int('7') returns integer 7. All convert strings to integers. eval() executes code (dangerous), string.atoi() deprecated (Python 2), int() preferred modern method. Use int() for string-to-integer conversion.

List comprehension: [expression for item in iterable if condition]. Concise list creation. Example: squares = [x**2 for x in range(10)]. Optional if filter. Equivalent to loop but more readable. Can nest: [[y for y in row] for row in matrix]. Efficient, Pythonic pattern.

Use random.sample(population, k) for k unique random elements. Example: random.sample(range(100), 10). No replacement. Returns list. k <= len(population). Sampling without replacement.

Default SimpleHTTPServer port is 8000. Python 2: python -m SimpleHTTPServer 8000. Python 3: python -m http.server 8000. Starts web server serving current directory. Access via http://localhost:8000. Default port 8000 if not specified. Quick file serving utility.

Value of a is 3. Statement a=(1,2,3) creates tuple. a=a[2] assigns third element (index 2, zero-based) to a. Tuple (1,2,3) has indices 0,1,2 with values 1,2,3. a[2] accesses element at index 2 which is 3. Reassignment changes a from tuple to integer 3.

Output: [2, 2, 2]. Closure captures p but evaluation delayed. Loop completes with p=2. All lambdas reference same p. When list comprehension executes, p=2 for all. Result: [lambda x: x+2] * 3 essentially. Each returns 1+2=2. Late binding closure pitfall.

Use random.random() for random float [0.0, 1.0). Example: r = random.random(). Uniform distribution. random.seed(n) for reproducibility. Basic random number generation.

Output: True. Tuple comparison lexicographic (element-by-element). (1,2,3) vs (1,2,4): first elements equal (1==1), second equal (2==2), third 3<4, so (1,2,3) < (1,2,4) is True. Compares left-to-right until difference found. First differing element determines result.

Value of f is filter object (iterator) containing permutations where first element is even. permutations([1,2]) generates [(1,2), (2,1)]. filter() keeps (2,1) where 2%2==0. Result: iterator with single tuple (2,1). Filter applies lambda to each permutation.

Use os.getcwd() to get current working directory. Returns absolute path string. Example: cwd = os.getcwd(). os.chdir(path) changes directory. Essential for relative path resolution. Directory context retrieval.

Use math.log(x, base) for logarithm. Default base e (natural log). Example: math.log(8, 2) = 3.0. math.log10(x) for base 10. math.log2(x) for base 2. Logarithm functions.

String formatting methods: % operator (old style), .format() method, f-strings (Python 3.6+). Example: '%s is %d' % (name, age), '{} is {}'.format(name, age), f'{name} is {age}'. F-strings fastest and most readable. .format() more features. % deprecated but common in legacy code.