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PCAP > Practise qus > Flashcards

Practise qus Flashcards

1
Q

Class A:
A = 1
def __init__(self):
self.a = 0

print(hasattr(A,’a’)

A

False

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2
Q

try:
raise Exception
except:
print(‘c’)
except Exception:
print(‘b’)

A

Syntax Error

as except should be last branch

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3
Q

try:
raise Exception(1,2,3)
except Exception as e:
print(len(e.args))

A

3

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4
Q

Class A:
def __init__(self, v):
self.__a = v+1

a = A(0)
print(a.__a)

A

Attribute Error

__a private so have to be called like

_A__a

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5
Q

class A:
def a(self):
print(‘a’)

class B:
def a(self):
print(‘b’)

class C(B,A):
def c(self):
self.a()

o = C()
o.c()

A

b

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6
Q

try:
raise Exception
except BaseException:
print(‘c’)
except Exception:
print(‘b’)
except:
print(‘h’)

A

c

Base Exception is main exception

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7
Q

assert var != 0

A

will stop the program when var == 0

as raises exception with var !=0 == False

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8
Q

my_str = ‘race’

my_str = my_str.copy()

A

AttributeError

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9
Q

my_str = ‘race’

my_str = my_str.insert(3,q)

A

Error

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10
Q

for i in range(10):
pass

print(i)

A

9

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11
Q

list1= [i for i in range(1,10)]
list2 = list1[-1:1:-1]

A

[9, 8, 7, 6, 5, 4, 3]

Remember the end range value is not included therefore the list reverses and stops at index = 2

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12
Q

Can tuples store tuples?

A

yes

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13
Q

Can tuples store lists?

A

yes

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14
Q

What can you deduce from the following statement?
(Select two answers)
str = open(‘file.txt’, “rt”)

a) str is a string read in from the file named file. txt
b) a new line character translation will be performed during the reads
c) if file. txt does not exist, it will be created
d) the opened file cannot be written with the use of the str variable

A

b,d

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15
Q

The first parameter of each method:

A

a) holds a reference to the currently processed object

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16
Q

i = 5
while i>0:
i = i//2
if i % 2 = 0:
break
else:
i+=1
print(i)

A

should be:

i % 2 == 0

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17
Q

i = 9
i =+ 2

What does i equal?

A

2

as i = +2
just means i equals positive 2

to add you need +=

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18
Q

for i in range(1,3):
print(‘ * ‘,end=’’)
else:
print(‘ * ‘)

A

Star star star
* * *

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19
Q

def f(n):
for i in range(1,n+1):
yield I

print(f(2))

_______________________________________
def f(n):
for i in range(1,n+1):
yield I

print([i for i in f(2)])

What is the difference in these two outputs? What do you need to remember?

A

<generator object f at 0x7f53e1f7fc10>

__________________________

NameError as I is not defined

you need to loop through generators

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20
Q

How many stars () does the snippet print?
s = ‘****’
s = s - s[2]
print(s)

A

Error

strings support concatenation. ‘-‘ is not supported in strings

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21
Q

Which can you do to this tuple: tup = ()
a) tup[:]
b) tup.append(0)
c) tup[0]
d) del tup

A

a and d

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22
Q

issubclass(B,B)

A

True

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23
Q

class C():
Z = 15
def __init__(self):
self.c = 2
def multiplier(self):
self.c *= 2

y = C()
x = C()
x.multiplier()
y.multiplier()
y.multiplier()
print(x.c)

A

4

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24
Q

class C():
Z = 15
def __init__(self):
self.c = 2
def multiplier():
self.c *= 2

y = C()
x = C()
x.multiplier()
y.multiplier()
y.multiplier()
print(x.c)

A

Type error as no self parameter in multiplier

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25
Q

class A:
X=0
def __init__(self):
self.x = 5

class B(A):
Y=1
def __init__(self):
self.y = 7

a = A()
b = B()

Which of the following do NOT output False?

A. isinstance(A,A)

B. isinstance(A.X,A)

C. isinstance(b,A)

D. isinstance(a,A)

E. isinstance(B,b)

A

C. isinstance(b,A) Ture

D. isinstance(a,A) True

E. isinstance(B,b) Error

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26
Q

When will isinstance() error?

A

When the second argument is not a class

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27
Q

‘a’*0

A

’’

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28
Q

len(234)

A

TypeError: object of type ‘int’ has no len()

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29
Q

1//2

A

0

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30
Q

-1//2

A

-1

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31
Q

class C():
__C=3

def \_\_string_amplify(self,char='b',times=1):
    self.a += char*times

c = C()
c.__string_amplify(‘d’, 2)

A

Error

needs to be c._C__string_amplify(‘d’, 2)

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32
Q

LOOK OUT FOR PRIVATE VARIABLES!!!!!!

CAN ONLY CALL THEM _CLASS__VARIABLE

A
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33
Q

How do you make a class an exception?

A

class my_exception(Exception)

my exception is now a subclass of Exception

you can raise it now

can make it a subclass of any Error, e.g. LookUpError

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34
Q

class A():
pass
class B(A):
pass
class C(A):
pass
class D(C,B,A):
pass

D.__bases__

A

(__main__.C, __main__.B, __main__.A)

This is a tuple and contains the classes not just the names

35
Q

class A():
pass
class B(A):
pass
class C(A):
pass
class D(C,B,A):
pass

D.__bases__[1].__bases__[0].__bases__

A

(object,)

A is the root class, so its base is type object

36
Q

class A:
def __init__(self):
pass

a = A(1)
print(hasattr(a,’A’))

Output?

A

Error

__init__ has no argument

37
Q

class A:
def __init__(self):
pass

a = A()
print(hasattr(a,’A’))

A

False

38
Q

class Ex(Exception):
def __init__(self,msg):
Exception.__init__(self,msg +msg)
self.args = (msg,)

try:
raise Ex(‘ex’)
except Ex as e:
print(e)

A

ex

39
Q

listy = [x for x in range(5)]
listy = list(filter(lambda x: x-3 and x-1,listy))

A

[0,2,4]

40
Q

hasattr(str,’__iter__’)

A

True

41
Q

What element can you not iterate through?

A

integers and floats

42
Q

lambda x: x*2 if hasattr(x, ‘__iter__’) else x**2, [‘ku’, 9, [3,8,3], (2,)]

A

[‘kuku’, 81, [3,8,3,3,8,3], (2,2)]

43
Q

def update_dict():
dict2 = {‘R’:’Best Language’}
dict2.update({‘Python’:’Second best’})
return lambda: dict2

How do you print the dict2?

A

print(update_dict()())

or update_dict()()

44
Q

def update_dict():
dict2 = {‘R’:’Best Language’}
dict2.update({‘Python’:’Second best’})
return lambda: dict2

fun = update_dict()
How do you print the dict2?

A

fun()

or print(fun())

45
Q

What does os.chdir(“..”) mean?

os.chdir(“./folder2/subfolder1”)
os.chdir(“..”)
os.getcwd()

A

os.chdir(“..”) goes up one folder- folder 2

’./’ means parent directory
‘..’ move to parent folder (move one level up)

46
Q

f = open(‘file.txt’, ‘a+b’)

A

We opened the file stream in binary, to be appended and updated

47
Q

What is the difference between a and + ?

A

updating is updating/changing existing data

a is just adding data

  1. What do we want to do with the file?
    ## r - reading (DEFAULT)
    ## w - writing (go to byte 0) – adding data
    ## a - appending (go to byte -1) – adding data
    ## x - exclusive creation – adding data
  2. Do we want to change its contents?
    ## NO: We don’t need to add anything (DEFAULT)
    ## YES: + (update) – changing data
  3. How do we want to read it?
    ## b = binary format
    ## t = text format (DEFAULT)
48
Q

We opened the file stream in binary, to write, read or update?

A

‘w+b’

49
Q

a = [1]
b=a[:]
a[0]=0

b?

A

1

This works for LISTS

50
Q

a = [1]
b=a
a[0]=0

b?

A

0

This works for LISTS

51
Q

Can you do this ‘python’.sort()?

A

NOOOOOOOOOO

sort() is for lists

52
Q

import sys
sys.path

Output?

A

list of strings

[‘/content’,
‘/env/python’,
‘/usr/lib/python38.zip’,
‘/usr/lib/python3.8’,
‘/usr/lib/python3.8/lib-dynload’,
‘’,
‘/usr/local/lib/python3.8/dist-packages’,
‘/usr/lib/python3/dist-packages’,
‘/usr/local/lib/python3.8/dist-packages/IPython/extensions’,
‘/root/.ipython’]

53
Q

‘python’.index(‘th’)

A

2

54
Q

sorted(‘python’)

A

[‘h’, ‘n’, ‘o’, ‘p’, ‘t’, ‘y’]

55
Q

uname_result(system=’Linux’, node=’e7c812d8a0e6’, release=’5.10.147+’, version=’#1 SMP Sat Dec 10 16:00:40 UTC 2022’, machine=’x86_64’, processor=’x86_64’)

platform.uname()

Linux-5.10.147+-x86_64-with-glibc2.27

platform.platform()

A
56
Q

Second argument of hassatr is a ….

A

string

57
Q

Second argument of isinstance is

A

class variable name (not a string)

58
Q

l =[0,1,2,3]
l[:3]

A

[0,1,2]

59
Q

pair1 = (‘a’,’b’,’c’)
pair2 = (‘d’,’e’,’f’)
index = 0

while index < len(pair1):
for item in pair2:
print(pair2[index] , item)
index += 1

A

d d
d e
d f
e d
e e
e f
f d
f e
f f

60
Q

val = ‘2’ or 1
val *= 3
print(val)

A

‘222’

61
Q

val = 1 or ‘2’
val *= 3
print(val)

A

3

62
Q

num = 12
num2 = num
num = num + 1
print(num2)

A

12

Integer

63
Q

Bytes are immutable
Slicing a bytes object returns a bytes object

A
64
Q

class A:
A=1
def __init__(self):
self.a = 0

print(hasattr(A,’a’))

A

False

65
Q

’’ in ‘ ‘

A

True

66
Q

not []

A

True

67
Q

not ‘’

A

True

68
Q

not 0

A

True

69
Q

class Class_A:
def __init__(self,var):
return var

obj = Class_A(20)
print(obj)

A

Error

__init__ cannot return a value

70
Q

i = 0
while i <4:
print(i, end=’-‘)
i +=1.5
if ((i<4) == False):
break
else:
print(0, end=’ ‘)

A

0-1.5-3.0-

as i is 4.5 before if statement within while loop so - is printed when i = 3

then i =4.5 and loop is broken with break

71
Q

turning a dictionary into a list…

A

creates a list of the keys

cannot change back

72
Q

i = ‘ ‘
for i in ‘ ‘:
print(‘python’,end=i)

A

pythonpythonpythonpythonpythonpython

for i in ‘number of spaces’

73
Q

i = ‘ ‘
while i in ‘ ‘:
print(‘python’,end=i)

A

pythonpythonpythonpythonpythonpython………………..infinte

while creates infinite loop

74
Q

class A:
A=1
def __init__(self):
self.b = 0

class B(A):
B=1
def __init__(self):
self.b = 5
A.__init__(self)

obj = B()
obj.b

A

0

as A.__init__(self) is after self.b =5 the self.b = 0 in class A overrides it

75
Q

li = [1,2,3,4,5,6]
li[-100:]

A

[1,2,3,4,5,6]

76
Q

int(‘100’,2)

int(‘0b100’,2)

A

4

base 2 so binary 100

first argument has to be string

77
Q

{2+3}*5

A

Error

cant multiply set

78
Q

(2+3,)*5

A

(5, 5, 5, 5, 5)

79
Q

class calc:
A = 20
B = 20
def __init__(self,a,b):
A = a
B= b
print(self.A + self.B)

calc(4,5)

A

40

as the variables in the __init__ don’t do anything they are not assigned to instance or class variables

80
Q

from math import *

dir(math)

A

Name Error

we have not imported math, we have imported maths contents

81
Q

What does Python Standard Library contain?

A

Storage space for the base Python packages and types

82
Q

Print(True or False)

A

True

83
Q

Print(True and False)

A

False

84
Q

l = [[c for c in range(r)] for r in range(3)]

A

[[], [0], [0, 1]]

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