PCAP Strings — 40 Questions

Question 1

A log analysis script needs to extract all IP addresses from a string. The IPs are in dotted-decimal format. Which regex pattern will correctly extract them?

Accepted Answer

r'\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}'. Both B and C match four octets of 1–3 digits separated by periods and will correctly extract IPs from a string. Option A contains an erroneous space, and option D allows octets of any length. Since the question asks for a pattern that correctly extracts, both B and C are valid; a single correct answer cannot be justified.

Answer

r'[0-9]+\. [0-9]+\.[0-9]+\.[0-9]+'

Answer

r'\d+\.\d+\.\d+\.\d+'

Question 2

Given the string s = 'Hello World!', which expression returns a list of characters?

Accepted Answer

list(s). The `list()` constructor, when passed a string, iterates over each character in the string and returns a list where each element is a single character. For `s = 'Hello World!'`, `list(s)` produces `['H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd', '!']`, which is exactly a list of characters.

Answer

s.split('')

Answer

s.split()

Answer

s.split(' ')

Question 3

Which of the following is the correct way to format a string with variables?

Accepted Answer

f'Name: {name}, Age: {age}'. Option C uses an f-string (formatted string literal), the modern recommended way in Python 3.6+ to embed variables directly into strings. Option A uses old-style % formatting, which is syntactically correct but outdated and less readable, so it is not the best modern approach. Option B is incorrect because .format() with named placeholders like {name} requires keyword arguments (e.g., .format(name=name, age=age)); passing positional arguments without indices will raise a KeyError. Option D is incorrect because it swaps the positional indices, so it would put age in place of name and vice versa.

Answer

'Name: %s, Age: %d' % (name, age)

Answer

'Name: {name}, Age: {age}'.format(name, age)

Answer

'Name: {0}, Age: {1}'.format(age, name)

Question 4

Which of the following methods can be used to check if a string starts with a vowel?

Accepted Answer

s.startswith(('a','e','i','o','u')). The `str.startswith()` method accepts a tuple of prefixes to check against. When a tuple is passed, Python checks if the string starts with any of the elements in the tuple, making it the proper way to test for multiple vowel prefixes in a single call.

Answer

s[0] in 'aeiou'

Answer

s.startswith('a','e','i','o','u')

Answer

s.startswith('a') or 'e' or 'i' or 'o' or 'u'

Question 5

Given s = 'Hello
World!

', what is the length of string s?

Accepted Answer

18. The string s = 'Hello
World!

' contains 7 newline escape sequences: one after 'Hello' and six after 'World!'. Each 
 is a single character. Counting: H(1), e(2), l(3), l(4), o(5), 
(6), W(7), o(8), r(9), l(10), d(11), !(12), then the six additional newlines (13-18). Total length = 18. A common mistake is to miscount the newline escapes or to treat 
 as two characters; if you treated all 7 
 as two characters, the length would be 25, not 19.

Answer

16

Answer

17

Answer

19

Question 6

Which THREE of the following are valid ways to create a string in Python?

Accepted Answer

'world'. All five options are valid ways to create a string in Python. 'world' (A) is a single-quoted string literal, str(['h','i']) (B) uses the str() constructor to convert a list into its string representation ''['h', 'i']'', '''multi-line''' (C) is a triple-quoted string literal, str(None) (D) converts the None object into the string 'None', and 'hello' (E) is a double-quoted string literal. The str() function returns a string for any argument, making B and D just as valid as the literals A, C, and E.

Question 7

What is the output of the following code?

import re
text = "Contact support@example.com for help or sales@example.org for sales."
pattern = r'\b\w+@\w+\.\w{2,4}\b'
result = re.findall(pattern, text)
print(result)

Accepted Answer

['support@example.com', 'sales@example.org']. The code (not shown) likely uses `re.findall()` with a pattern similar to `r'\b\w+@\w+\.\w{2,4}\b'`, which matches valid email addresses with 2-4 character top-level domains. The correct output would be a list of all matching email addresses from the input string. Option C is correct because it lists both 'support@example.com' and 'sales@example.org', which both satisfy the pattern. Options A, B, and D are incorrect as they either miss one valid address or return an empty list.

Answer

['support@example', 'sales@example']

Answer

[]

Answer

['support@example.com']

Question 8

Drag and drop the steps to install a third-party package using pip in Python into the correct order.

Accepted Answer

Open a terminal/command prompt, then verify pip is installed by running 'pip --version', then install the package using 'pip install package_name', then verify the installation by importing the package.. Installing a package with pip involves opening terminal, checking pip, using install command, optionally specifying version, and verifying.

Answer

Install the package using 'pip install package_name', then verify the installation by importing the package, then open a terminal/command prompt, then verify pip is installed.

Answer

Verify pip is installed, then open a terminal/command prompt, then verify the installation by importing the package, then install the package.

Answer

Open a terminal/command prompt, then install the package, then verify the installation, then check if pip is installed.

Question 9

A function receives a string and needs to return a new string with all vowels removed. Which code snippet accomplishes this efficiently?

Accepted Answer

return ''.join([c for c in s if c.lower() not in 'aeiou']). Option B uses a list comprehension that normalizes each character to lowercase before checking against 'aeiou', so it removes both 'A' and 'a'. This correctly removes all vowel characters regardless of case, while still running in O(n) time. Option C's str.translate with deletion string 'aeiou' only removes lowercase vowels and leaves uppercase vowels untouched.

Answer

for v in 'aeiou': s = s.replace(v, '')

Answer

return s.translate(str.maketrans('', '', 'aeiou'))

Answer

return re.sub('[aeiou]', '', s, flags=re.I)

Question 10

Refer to the exhibit. What is the output?

Accepted Answer

100. The code `print('100')` outputs the string `100` without quotes. In Python, `print()` displays the value passed to it; when a string literal is passed, it prints the characters of the string, not the surrounding quotes. Therefore, the output is `100` (the integer-like string, but as a string). Option B is correct because it shows the numeric value without quotes, which is how Python's `print()` renders a string.

Answer

'100'

Answer

True

Answer

Error

Question 11

A developer needs to extract the domain name (e.g., 'example.com') from an email address stored in the variable 'email'. The code currently uses `email.split('@')[1]`, which returns the domain part. However, it fails for addresses containing an '@' character in the local part (e.g., 'user@name@domain.com'). Which approach correctly extracts the domain assuming the email is valid?

Accepted Answer

email.rsplit('@', 1)[1]. `rsplit('@', 1)` splits the string from the right, limiting the split to one occurrence, so it always returns the last part after the final '@' character. This correctly extracts the domain even when the local part contains an '@', as in 'user@name@domain.com', where the domain is 'domain.com'.

Answer

email.partition('@')[0]

Answer

email.split('@')[1]

Answer

email.split('@', 1)[1]

Question 12

A developer encounters an error: `ValueError: Unknown format code 's' for object of type 'int'` when running `print("{0:s}".format(42))`. What is the problem and how should it be fixed?

Accepted Answer

Wrap 42 in str(): `print("{0:s}".format(str(42)))`. Both changing the format specifier to 'd' and wrapping the argument in str() resolve the ValueError. The explanation only justifies D and incorrectly implies D is the only correct fix.

Answer

Change `{0:s}` to `{0:str}` to explicitly specify string conversion.

Answer

Change `{0:s}` to `{0:i}` to indicate integer.

Question 13

Given `s = 'Python'`, what is the result of `s[-4::-1]`?

Accepted Answer

'tyP'. The slice `s[-4::-1]` starts at index -4 (which corresponds to the character 't' in 'Python') and proceeds backward to the beginning of the string because the step is -1. This extracts 't', 'y', 'P', resulting in 'tyP'. Option D is correct because it matches this exact backward traversal from index -4 to the start.

Answer

'ty'

Answer

'tho'

Answer

'nohtyP'

Question 14

Which TWO of the following expressions yield the substring 'Py' from the string s = 'Python'?

Accepted Answer

s[0:-4]. S[0:-4] uses negative indexing to slice from index 0 up to (but not including) index -4, which corresponds to the character 'o' (the fifth character from the end). Since 'Python' has length 6, index -4 is the character at position 2 (0-based), so the slice returns characters at indices 0 and 1, which are 'P' and 'y', yielding 'Py'.

Answer

s[0:2:2]

Answer

s[-6:-3]

Answer

s[0:1]

Question 15

Refer to the exhibit. What is the output?

Accepted Answer

18. The code prints the length of the string 'Python programming', which includes the space between 'Python' and 'programming', resulting in 18 characters. Therefore, the output is 18.

Answer

20

Answer

17

Answer

19

Question 16

Refer to the exhibit. What is printed?

Accepted Answer

'     Alice is 025 years old.'. The Python code uses an f-string with the format specifier `:>10s}` for the name and `:03d}` for the age. The `>10s` right-aligns the string 'Alice' in a field of width 10, producing 5 leading spaces. The `03d` formats the integer 25 as a zero-padded three-digit string '025'. The final output is `'     Alice is 025 years old.'`.

Answer

'     Alice is 25 years old.'

Answer

'Alice      is 25 years old.'

Answer

'     Alice is 25 years old.'

Question 17

A developer wrote a script that processes user input. The script expects a string containing a list of comma-separated values. The user enters "apple, banana, cherry, date". The script uses split() to separate the items. Which code correctly extracts the second item without leading/trailing spaces?

Accepted Answer

items = data.split(", "); second = items[1]. Both B and C correctly extract the second item without leading/trailing spaces. B splits on ', ' to get ['apple', 'banana', 'cherry', 'date'] and accesses index 1. C splits on ',' to get ['apple', ' banana', ' cherry', ' date'], then applies .strip() to items[1], yielding 'banana'. Since the question asks for correct extraction without specifying a preferred method, C is also correct.

Answer

items = data.split(); second = items[1]

Answer

items = data.split(","); second = items[2].strip()

Question 18

In a data processing pipeline, a string variable 'text' contains the value "Hello
World
". The developer needs to count the number of lines in the text. Which expression returns the correct line count (treating 
 and 
 as line terminators)?

Accepted Answer

text.count('
'). For text = "Hello
World
", text.count('
') equals 2 and len(text.splitlines()) equals 2. Since the question asks which expression returns the correct line count for the given value, both A and B are correct. The question needs revision to have a unique answer, e.g., by using a string that does not end with a newline.

Answer

text.count('
') + text.count('
')

Answer

len(text.split('
'))

Question 19

A function is supposed to return True if a string contains only digits, and False otherwise. Which implementation uses a Python string method correctly?

Accepted Answer

return s.isdigit(). `s.isdigit()` returns True if the string is non-empty and all characters are digit characters as defined by Python (including Unicode digits such as superscripts). It differs from `isdecimal()`, which only accepts decimal digits (0-9), and `isnumeric()`, which accepts any numeric character (including fractions, Roman numerals). The expression `s.isalnum() and not s.isalpha()` would incorrectly accept non-digit numeric characters like fractions.

Answer

return s.isdecimal()

Answer

return s.isnumeric()

Answer

return s.isalnum() and not s.isalpha()

Question 20

Given: s = "Python". Which expression raises an IndexError?

Accepted Answer

s[6]. For s = 'Python', valid positive indices are 0..5, so s[6] is out of range and raises IndexError. Valid negative indices are -1..-6, so s[-10] is also out of range and raises IndexError. Thus both B and C are correct.

Answer

s[-1]

Answer

s[5]