Basics

Question 1

Range

Answer 1

Immutable sequence
range(stop)
range(start, stop[, step])
start=0
step=1
<class ‘range’>
if step=0: ValueError
Only integers
no concatenation and repetition

Question 2

Slice

Answer 2

start=0
stop=len(x)
step=1

if step<0:
start=-1
stop=-len(x)-1

if step=0: ValueError

list[slice(start, stop, step)]
.indices(length)

Question 3

Extended slice

Answer 3

slice with a step

Question 4

Expression

Answer 4

produce a value
list comprehension
conditional (ternary) expression
yield x

Question 5

Statement

Answer 5

do something
return, pass, assert, raise

Question 6

List comprehension

Answer 6

[expr for item in iterable if cond]
multiple ifs: if cond1 if cond2

Question 7

Iterable Unpacking

Answer 7

a, b, c = 1, 2, 3
_ — throw-away
tuple = tuple

Question 8

Dictionary comprehension

Answer 8

{key: value for (key, value) in iterable}
<key if else>: <value if else>
PEP 274

Question 9

Unpacking inside tuple, list, set, dict

Answer 9

*range(n),
[*range(n)]
{*range(n)}
{**{'a': 1}}

PEP 448

Question 10

Throwaway variable

Answer 10

_

Question 11

Pass by Assignment

Answer 11

pass by reference
pass by object reference
pass by sharing

no primitive types
nothing is copied

Question 12

Docstrings

Answer 12

”"”triple double quotes”””
.__doc__

string literal
first statement in a module, function, class, method
PEP 257

Question 13

F-Strings

Answer 13

formatted string literals
~~~
{f_expr[=][!<conversion>][:<format_spec>]}
~~~</format_spec></conversion>

conversion flags

self-documenting expression
» f’{expr=}’
expr=value

format specifiers
PEP 498

Question 14

Modulo Operator

Answer 14

<format_string> % <values>

conversion specifier:

%[<flags>][<width>][.<precision>]<type>

tuple, dictionary

logging
dictionary interpolation

Question 15

str.format()

Answer 15

<template>.format(<args>, <kwargs>)

replacement fields
indices, keyword arguments

{[<name>][!<conversion>][:<format_spec>]}

localization
dictionary interpolation

Question 16

Special Method

Answer 16

method that is called implicitly by Python to execute a certain operation on a type
__method__

Question 17

Namespace

Answer 17

mapping from names to objects
no relation between names in different namespaces

global, local – dictionary
globals()
locals()

Question 18

Scope

Answer 18

textual region of a Python program where a namespace is directly accessible

values have no scope

Question 19

Del

Answer 19

unassignment statement
del ref_1[, ref_2…]

Reference:
- identifier
- index
- slice
- key
- attribute or method

from left to right
can’t delete built-in names

Question 20

Nested Unpacking

Answer 20

a, (b, c) = 1, [2, 3]

Question 21

Extended Unpacking

Answer 21

catch-all unpacking

a, b, *c = 1, 2, 3, 4

starred expression
only one
returns list
can be empty
must be in a list or tuple
PEP 3132

Question 22

Slice Assignment

Answer 22

s[i:j:k] = t

replace

delete
s[i:j] = []

insert
s[i:i] = t
s[len(s):] = t append
s[:0] = t prepend

if step not 1, must be same length

Question 23

Else Loop

Answer 23

executes if loop completes without break

for ... in ...:
    ...
else:
    ...

while ...:
    ...
else:
    ...

Question 24

Format Specification Mini-Language

Answer 24

standard format specifier:

[[<fill>]<align>][<sign>][z][#][0][<width>][<group>][.<prec>][<type>]

fill
align
sign
width
grouping_option
precision
type

Question 25

Conversion Flags

Answer 25

!s str()
!r repr()
!a ascii()