Python

Question 1

What is snake case in python?

Answer 1

Using underscores to form a long variable name

Question 2

What is the type of the result of a division operation in python?

Answer 2

floating point

Question 3

How do you get integer value out out of a division in python?

Answer 3

By using the ‘//’ operator

Question 4

Does // operator do a round-off?

Answer 4

No

Question 5

How do you distinguish between a variable definition and further use in python?

Answer 5

You can’t, both have same syntax

Question 6

f-strings are available from which python version?

Answer 6

3.6 onwards.

Question 7

What are f-strings?

Answer 7

A convenient way to format different types into string

Question 8

What is another way (than f-strings) to format strings without explicitly converting them?

Answer 8

By having placeholders in the string with “{}” and calling the format method of the string with requisite parameters

Question 9

What is the constraint on the number of parameters for the format method of the string?

Answer 9

It can be more, but cannot be less

Question 10

In what ways “format” can take parameters for a string?

Answer 10

format can take parameters as positional as well as keyword based.

Question 11

How does “format” method take keyword based arguments?

Answer 11

keyword based arguments have to be given in the last after positional arguments. They cannot be mixed.

Question 12

What is necessary for passing keyword based arguments to “format” method of string?

Answer 12

The string should contain the keyword in { } in it

Question 13

Is string.format(name=name) valid? Both identifiers

Answer 13

Yes, the first one will be looked for in the string, while the second one is treated as a proper variable

Question 14

How does f-string and format compare?

Answer 14

• f-string takes actual parameters, while format takes formal parameters (which is to be filled in by passing format with actual parameters)
• f-string can take expressions that evaluate to a value, while format cannot

Question 15

Which function in python reads input from keyboard and returns a string?

Answer 15

input(“message”)

Question 16

What are boolean keywords in python?

Answer 16

True and False

Question 17

What does print take?

Answer 17

An expression that can be evaluated

Question 18

What are python’s boolean operators?

Answer 18

and, not, or

Question 19

What does and/or return?

Answer 19

• and returns first value if it is false, otherwise it returns the second value
• or returns the first value it is true, otherwise it returns the second value

Question 20

What does not return?

Answer 20

not always returns True or False

Question 21

What does list.remove() take?

Answer 21

The value of the element which needs to be removed from the list

Question 22

Is parens mandatory for writing tuples?

Answer 22

No

Question 23

How to minimally express a tuple of only one item?

Answer 23

a,

Question 24

How do you add a new element to a tuple variable?

Answer 24

By adding “+” another tuple of single element to the variable: v = v + (e,)

Question 25

How do we represent set1 - set2 in python?

Answer 25

set1.difference(set2)

Question 26

How do we represent symmetric difference between two sets (set1 U set2) - (set1 AND set2)

Answer 26

set1.symmetric_difference(set2)

Question 27

What type is “{}”

Answer 27

dict, not set

Question 28

How do we represent set intersection in python?

Answer 28

set1.intersection(set2)

Question 29

How do we represent set union in python?

Answer 29

set1.union(set2)

Question 30

How do we represent an empty set in python?

Answer 30

set()

Question 31

Does dictionary keep order of elements inserted?

Answer 31

Yes, in python 3.7

Question 32

How to make a dict from values?

Answer 32

Have a list of 2-element tuples and feed it to dict()

Question 33

A list of grades, a tuple of grades, a set of grades - which is not a correct choice

Answer 33

set of grades

Question 34

A list of grades, a tuple of grades - which is a better option?

Answer 34

if grades are not going to be added, a tuple is better, otherwise a list is better

Question 35

sum(), len() - can be used on which of the following data structures: set, list, tuple

Answer 35

all of them

Question 36

How come we can pass values and expressions to if or while in python?

Answer 36

Python implicitly passes all those expressions through bool to get True or False

Question 37

What is the else/if keyword in python?

Answer 37

elif

Question 38

What is the difference between while loop and for loop in python?

Answer 38

While loop runs an undefined number of times - based on an external event, and for loop runs for a defined number of times

Question 39

What is the difference between:
if a in b:
for a in b:

Answer 39

In the first one, “a” is a known identifier or a constant, while in the second one, “a” is a new identifier

Question 40

What is the act of taking a collection into more than one variable is called?

Answer 40

destructuring

Question 41

What does for d in dict give?

Answer 41

A list of all the keys

Question 42

How do you iterate over values of a dict?

Answer 42

dict.values()

Question 43

How do you destructure key, value from a dict?

Answer 43

dict.items()

Question 44

what does while-else/for-else statement do in python?

Answer 44

If for doesn’t encounter a break, then else clause will be executed, otherwise else clause will not be executed

Question 45

What is the difference between aList and aList[:]

Answer 45

The second one gives a new copy of aList

Question 46

what does aList[0] and aList[-1] represent?

Answer 46

The first and the last elements of the list

Question 47

what does aList[-x] represent?

Answer 47

xth element in the list starting from the last element with index as 1 towards left side

Question 48

how do you mathematically repreent aList[x:y]?

Answer 48

[x, y)

Question 49

What is the direction of slicing a list?

Answer 49

Always from left to right

Question 50

What happens if a list is sliced with indices pointing to elements from right to left?

Answer 50

An empty list is returned

Question 51

In aList[-x:-y], what is the constraint to get at least one element?

Answer 51

x > y

Question 52

How do you differently explain list comprehension?

Answer 52

Expression followed by the for statement with an optional if statement

Question 53

What is a readable way to write a list comprehension?

Answer 53

expression, for statement, if statement - each in one line

Question 54

Comprehension is applicable for which of the following collections? list, set, dict

Answer 54

All of them

Question 55

When you create a collection, think about _____

Answer 55

comprehension

Question 56

How do you create a list of tuples with lists to feed to dict()?

Answer 56

With a zip function

Question 57

Which is more simpler? a dict made out of comprehension or a dict made out of a zip?

Answer 57

dict made out of a zip

Question 58

When does a dict made out of comprehension make sense over a dict made out of zip?

Answer 58

When we want to conditionally add the list elements into the zip

Question 59

Does zip takes only two lists?

Answer 59

No, it can take more than two

Question 60

What happens if the lists given to zip are of different lengths?

Answer 60

zip will make a list of tuples of the size of the smallest list

Question 61

can the argument to a function be nameless?

Answer 61

Yes

Question 62

How is a variable resolved i.e. searched for resolution?

Answer 62

First in local scope, then in global scope

Question 63

What is the type of the value returned from a function which has no explicit return statement?

Answer 63

None

Question 64

What are the two types of arguments in python to a function?

Answer 64

positional and keyword arguments

Question 65

What is the constraint for passing positional and keyword arguments in python?

Answer 65

positional arguments should precede keyword arguments

Question 66

What is the constraint for defining a function with default and non-default parameters?

Answer 66

non-default parameters must precede default parameters

Question 67

What is the argument given to print to change what is printed between the arguments?

Answer 67

sep=xyz

Question 68

When are the default parameters for a function evaluated and stored?

Answer 68

At the time of function definition, not function invocation

Question 69

What are the consequences of having non-constant expressions as values for default parameters?

Answer 69

Any change in the variables will not change the value of default parameters and it becomes less readable

Question 70

What is the difference between a normal function and a lambda function?

Answer 70

Normal function is assigned to a variable with the function definition itself, where as lambda function has to be explicitly assigned to a variable through an assignment statement

Question 71

When is a function vs lambda destroyed in python?

Answer 71

When the function or lambda reference goes out of scope

Question 72

Can a lambda definition span more than one line?

Answer 72

No

Question 73

What happens when a lambda definition is not assigned to anything?

Answer 73

it is destroyed immediately

Question 74

How do you check for the presence of a key in dict?

Answer 74

with the “in” operator

Question 75

Which string method is used to validate if the string is a number?

Answer 75

isdigit(), isdecimal(), isnumeric()

Question 76

What is the difference between two string methods: isdigit() and isnumeric()

Answer 76

The latter works with unicode characters

Question 77

What is the no-op statement in python?

Answer 77

pass

Question 78

What happens if a function is defined two times?

Answer 78

The latest definition overrides the old definition

Question 79

What is a clean and extensible way to implement a menu of options to be selected by the user?

Answer 79

A dictionary with key as the supported options and values as the function handlers

Question 80

How does lambda functions help write generic code

Answer 80

It helps by the caller pass the paramater(object) as is to the lambda function without interpreting the type of the parameter

Question 81

In the class definitions, is the “self” keyword mandatory?

Answer 81

No, the first parameter refers to the object and it can be named anything.

Question 82

What is the function that gets called first when a class is instantiated?

Answer 82

__init__

Question 83

__init__ is also called as?

Answer 83

dunder init function

Question 84

What are the different valid ways of calling an object method?

Answer 84

1. object.method()

2. class.method(object)

Question 85

How does the list of attributes in a class defined?

Answer 85

As and when they are assigned.

Question 86

Can a class attributes grow dynamically after object creation?

Answer 86

Yes

Question 87

List of arguments to python script is stored in?

Answer 87

sys.argv list

Question 88

Current OS is stored in?

Answer 88

sys.platform

Question 89

Name the fully qualified function to write to stdout

Answer 89

sys.stdout.write(str)

Question 90

Python version is stored in?

Answer 90

sys.version

Question 91

PATH contents are available in?

Answer 91

sys.path

Question 92

Function to check if a file exists in file system?

Answer 92

os.path.isfile()

Question 93

Function to check access permissions of a file?

Answer 93

os.access(file, os.)

Question 94

Function to list the contents of a directory?

Answer 94

os.listdir(dir)

Question 95

Function to get current working directory?

Answer 95

os.getcwd()

Question 96

Function to execute a shell command?

Answer 96

os.system()

Question 97

Function to walk the current directory?

Answer 97

os.walk()

Question 98

What does os.walk() return?

Answer 98

it returns the root directory (which is being walked), a list of directories and files in the root

Question 99

Function to check OS?

Answer 99

platform.system()

Question 100

What is the difference between sys.platform and platform.system() ?

Answer 100

sys.platform is an variable attribute, platform.system is a method attribute

Question 101

What are different ways to run a command?

Answer 101

os.system(), subprocess.run(), subprocess.call(), os.spawn(), os.popen() etc.

Question 102

When executing commands like “clear” through subprocess, what needs to be indicated?

Answer 102

shell=True

Question 103

What does subprocess.run() return?

Answer 103

An instance of CompletedProcess class

Question 104

What does subprocess.check_call() function return?

Answer 104

Nothing if the call succeeds, otherwise raises a CalledProcessError exception

Question 105

What does subprocess.check_output() function return?

Answer 105

Returns the output as a byte string if it exits normally otherwise raises CalledProcessError exception

Question 106

What does os.system() return?

Answer 106

the exit code of the process

Question 107

What does stdout=subprocess.PIPE mean?

Answer 107

Instead of pointing to standard output, stdout is now pointing to a pipe (which will be instantiated and returned)

Question 108

What does stdout=subprocess.PIPE, stderr=subprocess.STDOUT mean?

Answer 108

output is given a new pipe and err is redirected to stdout (to the new pipe here)

Question 109

Why subprocess.wait() needs to be used?

Answer 109

to let the child finish so as to collect output

Question 110

What does subprocess.communicate() return?

Answer 110

A tuple of (stdout, stderr)

Question 111

What is the general sequence of steps to spawn a process and collect its output with subprocess?

Answer 111

sp=subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
ret=sp.wait()
out, err = sp.communicate()
#check ret, out, err

Question 112

How to convert bytes to string?

Answer 112

str(, “UTF-8”) #encoding scheme

Question 113

How can “ps aux | grep xyz” be achieved in python with subprocess methods?

Answer 113

ps=subprocess.Popen([“ps”, “aux”], stdout=subprocess.PIPE)
grep=subprocess.check_output([“grep”, “xyz”], stdin=ps.output)
ret = ps.wait() #check return code

Question 114

Once a Popen object is created with PIPE, how can that be used elsewhere or assigned elsewhere?

Answer 114

we can refer to stdout, stdin of the Popen object

Question 115

When a command and its parameters is given as a string to subprocess.Popen(), what should shell=?

Answer 115

True, as it is passed as is to the shell to execute, without which it will fail

Question 116

With shell=True, what happens if we give command as a list of command, parameters?

Answer 116

The parameters are ignored and only the command is executed

Question 117

What is given to subprocess.Popen to get output and error as text (string) instead of byte object?

Answer 117

universal_newlines=True

Question 118

What are the 4 steps of argument parsing?

Answer 118

import argparse; create a parser; add arguments; parse arguments

Question 119

How is an argument parser created?

Answer 119

argparse.ArgumentParser

Question 120

What is the function in argparse to add an argument?

Answer 120

add_argument()

Question 121

How do we convert arguments passed to add_argument to different types?

Answer 121

with type=xyz

Question 122

How do we add description to an argument in add_argument?

Answer 122

with help=abc

Question 123

How do we validate that given input is within a specified list when adding an argument with add_argument?

Answer 123

with choices=[a, b, c]

Question 124

which kwarg specifies that an argument is mandatory or not in add_argument

Answer 124

required=True or required=False

Question 125

How are positional arguments in add_argument referred to in the code?

Answer 125

when we give dest=”xyz”, it is referred to with attribute xyz on the argumenr parser object

Question 126

How are optional arguments given a default value in add_argument of argparse?

Answer 126

with default=abc

Question 127

How are optional arguments added with

add_argument?

Answer 127

with a “-“ or with a “–”

Question 128

How are optional arguments referred to in the code?

Answer 128

the name given with “-“ or “–” or with a dest=abc

Question 129

How is a boolean flag specfied in add_argument of argparse?

Answer 129

with action=”store_true”

Question 130

When short and long names are given in add_argument of argparse, which one prevails?

Answer 130

long one

Question 131

Which function in argparse is used to create a set of mutually exclusive arguments?

Answer 131

add_mutualy_exclusive_group, group.add_argument()

Question 132

With argparse, how do we specify that an argument is a file that has to be read or written?

Answer 132

with type=argparse.FileType(‘r’) or type=argparse.FileType(‘w’, encoding=”UTF-8”)

Question 133

How do we import scapy into python code?

Answer 133

import scapy.all as scapy and call scapy.xxx()

Question 134

Which operator is used to stack different layers in a scapy constructed packet?

Answer 134

’/’ operator

Question 135

What denotes the latest result in python?

Answer 135

“_”

Question 136

Which function will omit showing default in scapy constructed packets?

Answer 136

hide_defaults()

Question 137

which scapy function is used to read pcap files?

Answer 137

rdpcap()

Question 138

Which scapy function is used to dump the packet in hex?

Answer 138

hexdump()

Question 139

Which scapy function is used to format the packet with a format specifier?

Answer 139

pkt.sprintf()

Question 140

Which scapy function is used to dump the packet in the command format (which can be executed to generate the same packet)?

Answer 140

pkt.command()

Question 141

Which scapy function is used to display the packet after proper processing (dns resolution, cheksum calculation etc.)

Answer 141

pkt.show2()

Question 142

In scapy, how to set a field to a range of values?

Answer 142

ttl=[1,2,(5, 9)]

Question 143

In scapy, when we give a range (a,b), is it inclusive or exclusive?

Answer 143

Inclusive

Question 144

In scapy, which function sends packets at layer 3?

Answer 144

send()

Question 145

In scapy, which function sends packets at layer 2?

Answer 145

sendp()

Question 146

In scapy, with send/sendp, which kwarg is used to get back the list of packets sent?

Answer 146

return_packets=True

Question 147

In scapy, which function is used to randomize the packet fields?

Answer 147

fuzz()

Question 148

In scapy, how is fuzz() used to randomize fields?

Answer 148

fuzz(IP()/UDP()) etc.

Question 149

In scapy, what all fuzz() can randomize and what it cannot?

Answer 149

Fields overridden by upper layers and fields that are not defaults - are not fuzzed

Question 150

In scapy, to randomize (fuzz) IP addresses which function should be used?

Answer 150

RandIP()

Question 151

In scapy, what does the send and receive family of functions return?

Answer 151

a couple of two lists - the first list is a couple of (sent, received packets), the second list is unanswered packets

Question 152

In scapy, in the send/receive family of functions what is the advantage of receiving unanswered packets in return?

Answer 152

We can call send/receive again with the unanswered list as is

Question 153

In scapy, in send/receive family of functions, what do the kwargs inter, retry and timeout mean?

Answer 153

inter - interval (in secs) between transmitting two packets
retry - if retry is x, then unanswered list is retransmitted “x” number of times. If the retry is -x, then the unanswered list is transmitted until the unanswered list is the same for the last x tries
timeout - when to start treating sent packets as unanswered

Question 154

In scapy, which function lists all the available packet types?

Answer 154

ls()

Question 155

In scapy, how do we see all the supported fields for a given packet type?

Answer 155

ls(pkt_type)

Question 156

In scapy, which function lists all the commands available?

Answer 156

lsc()

Question 157

In scapy, how do we see the help for a command?

Answer 157

help(cmd)

Question 158

In scapy, which function is used to write packets to a pcap file?

Answer 158

wrpcap()

Question 159

In scapy, which function is used to read packets from a pcap file?

Answer 159

rdpcap()

Question 160

In scapy, when we create a ICMP() packet, which type of the packet is created by default?

Answer 160

echo-request

Question 161

In scapy, how can we change the configuration on which scapy operates?

Answer 161

conf.xyz = abc;