Python

Question 1

Iterable protocol

Answer 1

iterables (implementing __iter__() )
iterators (implementing __next__() )
can be used in
for [var] in [iterable].

Functionaly equivalent to:
obj = train.\_\_iter\_\_()
name = obj.\_\_next\_\_()
do something with name
name = obj.\_\_next\_\_()
do something with name
... until IndexError is raised (?)

Question 2

‘with’ protocol

Answer 2

__enter__()

__exit__()

Question 3

Dictionary comprehension on prev dict

Answer 3

new_dict = {key:value for (key,value) in old_dict.items()}
new_dict = {key:value for (key,value) in old_dict.items()}

Question 4

Dictionary comprehension from scratch

Answer 4

{n:n**2 for n in numbers if n%2 == 0}

Question 5

Dictionary comprehension conditional val

Answer 5

{k:(‘even’ if v%2==0 else ‘odd’) for (k,v) in dict1.items()}

Question 6

Dictionary creation

Answer 6

dict_var = {key1:val1, key2:val2}

Question 7

Set creation

Answer 7

set_var = {val1, val2}

Question 8

List creation

Answer 8

list_var = [ val1, val2 ]

Question 9

Set comprehension

Answer 9

{s**2 for s in range(10)}

Question 10

List comprehension

Answer 10

[s**2 for s in range(10)]

Question 11

Lists vs Tuples

Answer 11

lists are for looping; tuples for structs. Lists are homogeneous; tuples heterogeneous. Lists for variable length.

Question 12

__name__ contents

Answer 12

“__main__” - if you run this script,

filename - if you import the script as a module.

Question 13

Override comparison

Answer 13

>>> class Whateva:
...     def \_\_eq\_\_(self, other):
...         return True

Question 14

REPL

Answer 14

== Interpreter.

Read, Evaluate, Print, Repeat.

Question 15

Equality vs Identity

Answer 15

'==' vs 'is'
contents equal (and overridable) , vs references the same object (non overridable)

Question 16

What’s mutable?

Answer 16

List, Dictionary, class: Mutable

Tuple, string, number: Immutable

Question 17

Test membership

Answer 17

> > > 3 not in [2, 3, 4]
False
(2, 3) in [(2, 3), (5, 6), (9, 1)]
True

Question 18

Override arithmetics

Answer 18

x + y invokes x.\_\_add\_\_(y)
x - y invokes x.\_\_sub\_\_(y)
x * y invokes x.\_\_mul\_\_(y)
x / y invokes x.\_\_truediv\_\_(y)
x ** y invokes x.\_\_pow\_\_(y)

Question 19

Overriding container methods

Answer 19

len(x) invokes x.__len__()
x[key] invokes x.__getitem__(key)
x[key] = item invokes x.__setitem__(key, item)
item in x invokes x.__contains__(item)
iter(x) invokes x.__iter__()
next(x) invokes x.__next__()

Question 20

Override print behavior

Answer 20

__str__ calls __repr__, override either one.

Question 21

self.__class__, self.__dict__

Answer 21

? TODO

Question 22

__eval__

Answer 22

? TODO

Question 23

ctor

Answer 23

__init__

Question 24

Brackets operator ()

Answer 24

__call__