Practice

Question 1

Remove an item from a list

Answer 1

Answer

Question 2

Reverse list

Answer 2

.reverse() in place, only for list

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

map(function, iterable)
map(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