Practice

Question 1

Remove an item from a list

Answer 1

Answer

Question 2

Reverse list

Answer 2

.reverse() in place

reversed() returns iterator
(if the input list changes iterator sees it)

[::-1] reversed copy, slow

Question 3

Sequence Functions

Answer 3

len()
min()
max()

Question 4

Functions that return iterator

Answer 4

reversed(), enumerate(), zip(), map(), filter()

Question 5

Generator Usage

Answer 5

infinite sequence

Question 6

Map

Answer 6

map(function, iterables)
transformation function
lambda function (don’t use!)

Question 7

Filter

Answer 7

filter(function, iterable)
filter(None, iterable) True elements
lambda function (don’t use!)

Question 8

Generator expression without ()

Answer 8

list(square(x) for x in numbers)

Question 9

Sum

Answer 9

sum(iterable, start)
start = 0
can’t sum strings

Question 10

Zip

Answer 10

zip(*iterables, strict=False)

strict=True raises ValueError if iterables have different length

dict(zip(keys, values))

Question 11

Enumerate

Answer 11

enumerate(iterable, start=0)

Question 12

Dictionary update()

Answer 12

dict.update(iterable or kwargs)
iterable: dict, iterable of tuples etc.

Question 13

Sort

Answer 13

sort(*, key=None, reverse=False)
list.sort()

Question 14

Max, Min

Answer 14

max(iterable, *, key=None)
max(iterable, *, default, key=None)
max(arg1, arg2, *args, key=None)

Question 15

All, Any

Answer 15

all(iterable)
True if iterable is empty

any(iterable)
False if iterable is empty

Question 16

Is Instance

Answer 16

isinstance(object, classinfo)
classinfo - type, tuple of types

Question 17

Sorted

Answer 17

sorted(iterable, /, *, key=None, reverse=False)
returns a list

Question 18

Dictionary Creation

Answer 18

• dict(dict1)
• dict(iterable of (key, value))
• merge: dict1 | dict2
• merge into a literal: {…, **dict1, …}

Question 19

Is Subclass

Answer 19

issubclass(class, classinfo)
classinfo - class, tuple of classes

is class a subclass of classinfo

Question 20

Size

Answer 20

import sys

sys.getsizeof(obj)

Question 21

Closure Usage

Answer 21

• function factories
• callbacks
• data encapsulation
• decorators
• memoization

Question 22

Raw String Literal

Answer 22

r'<string>'

treats backlslashes as literal characters

Question 23

Repr

Answer 23

repr(object)

returns a string containing a printable representation of an object

__repr__()

Question 24

Import

Answer 24

import module
import module as name
from module import var1, var2
from module import var1 as name1, var2 as name2

Question 25

Add

Answer 25

**x = x + 1** – .__add__() **x += 1** – .__iadd__()

Question 26

NamedTuple

Answer 26

namedtuple(typename, field_names, *, rename=False, defaults=None, module=None) returns a new tuple subclass named *typename* filednames – `['x, 'y']` or `'x y'` or `'x, y'` ``` from collections import namedtuple Point = namedtuple('Point', ['x', 'y']) p = Point(11, y=22) print(p.x, p[1]) ``` ._fields ._make(iterable) ._asdict() ._replace(**kwargs)

Question 27

Callable

Answer 27

callable(object) True if object appears callable, False if not

Question 28

Iterator Chain

Answer 28

one element at a time chain = iter2(iter1(...))

Question 29

str() vs repr()

Answer 29

str() for user repr() for developer

Question 30

Walrus Operator

Answer 30

NAME := expr assignment expression Python 3.8 PEP 572

Question 31

Send

Answer 31

generator.send(value) resumes generator and sends value to yield expression returns next yielded value, or raises StopIteration if done two-way communication next() with value coroutines, event-driven flows, stateful processes

Question 32

Throw

Answer 32

generator.throw(value) raises exception inside generator

Question 33

Close

Answer 33

generator.close() raises GeneratorExit inside generator at last yield returns value or None ends generator gracefully

Question 34

yield from

Answer 34

generator delegations delegates part of operations to another generator subgenerator PEP 380