PCAP Strings Practice Test 4 — 15 Questions

Question 1

You are a network engineer troubleshooting a script that processes router configuration files. The script reads a configuration line from a file: 'interface GigabitEthernet0/1
 ip address 192.168.1.1 255.255.255.0
 no shutdown'. The script needs to extract the interface name and IP address. The current code uses string split operations but fails when the line has extra spaces or tabs. For example, when the line is 'interface   GigabitEthernet0/1', the split returns ['interface', '', '', 'GigabitEthernet0/1'] and the script fails. You need to modify the script to robustly extract the interface name and IP address regardless of whitespace. Which approach should you take?

Accepted Answer

Use line.split() instead of line.split(' ').. `line.split()` without arguments splits on any whitespace (spaces, tabs, newlines) and automatically removes empty strings, making it robust against extra spaces or tabs. In contrast, `line.split(' ')` splits only on single space characters, leaving empty strings when multiple spaces or tabs are present. This behavior is defined by Python's string method documentation and is essential for parsing configuration files where whitespace is inconsistent.

Answer

Manually iterate and concatenate characters until a space is found.

Answer

Use line.split(' ') and then filter out empty strings.

Answer

Use line.startswith('interface') to identify the line, then extract substring.

Question 2

You are a data analyst working with a dataset of customer reviews. Each review is stored as a string in a list. You need to count how many reviews contain the word 'excellent' (case-insensitive). However, the word might appear as 'Excellent', 'EXCELLENT', or even with punctuation like 'excellent!'. The current code uses 'excellent' in review.lower(), but this fails if 'excellent' is part of another word like 'unexcellent'. You need to ensure that only the whole word 'excellent' is counted. Which code modification will correctly count whole word occurrences?

Accepted Answer

Use re.search(r'\bexcellent\b', review, re.IGNORECASE). `re.search(r'\bexcellent\b', review, re.IGNORECASE)` uses the `\b` word boundary anchor to ensure that 'excellent' is matched as a whole word, not as part of another word like 'unexcellent'. The `re.IGNORECASE` flag handles case-insensitive matching, covering 'Excellent', 'EXCELLENT', etc. This approach also correctly handles punctuation attached to the word, such as 'excellent!', because the word boundary matches between a word character and a non-word character.

Answer

Use 'excellent' in review.lower().split()

Answer

Use review.lower().count('excellent') > 0

Answer

Use review.lower().find('excellent') != -1

Question 3

A developer needs to parse a log file where each line contains a timestamp followed by a message. The timestamp format is 'YYYY-MM-DD HH:MM:SS'. Which string method is most appropriate to split the timestamp from the message?

Accepted Answer

str.split(). Str.split(), is the most appropriate because it splits a string on whitespace by default. Although the timestamp 'YYYY-MM-DD HH:MM:SS' contains a space, using split() without arguments returns a list of all space-separated elements. Since the timestamp is always the first two elements (date and time), the developer can join them with a space to get the full timestamp. Alternatively, split() can be used with a specified separator and maxsplit to achieve the desired split. This flexibility makes str.split() the best choice among the given options.

Answer

str.rsplit()

Answer

str.splitlines()

Answer

str.partition()

Question 4

A programmer writes a function that expects a string and returns it reversed. Which code snippet correctly reverses the string 'stressed' to 'desserts'?

Accepted Answer

result = s[::-1]. Both option B and option D correctly reverse the string 'stressed' to 'desserts'. Option B uses slice notation `[::-1]`, which creates a reversed copy of the string by stepping from end to start with a step of -1. This is the most direct and idiomatic way to reverse a string in Python. Option D uses `''.join(reversed(s))`: `reversed(s)` returns an iterator that yields characters in reverse order, and `join()` concatenates them into a new string. This is also a valid and correct approach. Option A is incorrect because strings do not have a `reversed()` method; `reversed()` is a built-in function. Option C is incorrect because `.reverse()` is a list method, not a string method, and strings are immutable.

Answer

result = s.reversed()

Answer

s.reverse()

Question 5

A developer is tasked with validating user input that must be a 10-digit phone number. The input may contain spaces, dashes, and parentheses. Which approach best ensures the input contains exactly 10 digits?

Accepted Answer

if len([c for c in s if c.isdigit()]) == 10:. Uses a list comprehension to filter only digit characters from the input string `s` and then checks if the count of those digits is exactly 10. This correctly handles any non-digit characters (spaces, dashes, parentheses) by ignoring them, ensuring the validation focuses solely on the presence of exactly ten digits.

Answer

if len(s) >= 10 and s.isdigit():

Answer

if s[:10].isdigit():

Answer

if s.isdigit() and len(s) == 10:

Question 6

When processing a large text file, a developer notices that using str.replace() in a loop is slow. Which alternative is most efficient for multiple replacements?

Accepted Answer

Use str.translate() with a translation table. `str.translate()` with a translation table built by `str.maketrans()` performs all character replacements in a single pass over the string, operating at the C level in CPython. This avoids the O(n) per-replacement overhead of `str.replace()` in a loop, making it the most efficient choice for multiple, fixed-character substitutions on large text.

Answer

Use str.maketrans() on the original string

Answer

Use re.sub() from the re module

Answer

Chain multiple str.replace() calls

Question 7

A developer needs to check if a string contains only alphanumeric characters. Which string method should be used?

Accepted Answer

s.isalnum(). The `isalnum()` method returns `True` if all characters in the string are alphanumeric (letters or digits) and the string is non-empty. This directly matches the requirement to check for only alphanumeric characters, covering both letters and digits without any other characters.

Answer

s.isnumeric()

Answer

s.isdigit()

Answer

s.isalpha()

Question 8

A programmer is writing a script to generate SQL queries safely. They need to escape single quotes in user-provided strings to prevent injection. Which approach is most robust?

Accepted Answer

s.replace("'", "''"). In SQL, single quotes are escaped by doubling them (''), not by using backslashes. This is the standard escape mechanism defined by the SQL standard (ISO/IEC 9075) and is supported by databases like PostgreSQL, SQLite, and Oracle. Using `s.replace("'", "''")` ensures that a single quote in user input becomes two single quotes in the SQL string, preventing injection while preserving the literal quote.

Answer

s.replace("\'", "'")

Answer

s.replace("'", "\'")

Answer

s.strip("'")

Question 9

A developer wants to remove leading and trailing whitespace from a string. Which method should be used?

Accepted Answer

s.strip(). The `strip()` method in Python removes both leading and trailing whitespace (including spaces, tabs, and newlines) from a string. This is the standard method for trimming whitespace from both ends, as specified in Python's string documentation.

Answer

s.lstrip()

Answer

s.trim()

Answer

s.rstrip()

Question 10

Which TWO of the following methods return a boolean value?

Accepted Answer

str.isspace(). The methods `str.isspace()` and `str.isalpha()` are both string methods that return a boolean value (`True` or `False`) based on whether the string meets specific character classification criteria. `isspace()` returns `True` if all characters in the string are whitespace, while `isalpha()` returns `True` if all characters are alphabetic.

Answer

str.upper()

Answer

str.split()

Answer

str.join()

Question 11

Which TWO of the following are immutable in Python?

Accepted Answer

Tuple. Tuple (B) is immutable because once created, its elements cannot be added, removed, or changed. This is enforced by Python's internal structure: tuples are stored as a fixed-length array of PyObject pointers, and any attempt to modify them raises a TypeError.

Answer

Set

Answer

Dictionary

Answer

List

Question 12

Refer to the exhibit. What is the output of the code?

Accepted Answer

Programming. The code likely uses slicing with a start index to extract 'Programming' from the string 'Python Programming'. For instance, 'Python Programming'[7:] returns the substring starting at index 7 (after 'Python ' which is 7 characters including space) to the end, which is 'Programming'. This operation is a common way to obtain a substring.

Answer

Program

Answer

Python Programming

Answer

Python

Question 13

Refer to the exhibit. What is the output?

Accepted Answer

HI, WORLD!. The code uses the `upper()` method on the string `'Hi, World!'`, which converts all lowercase letters to uppercase. The output is `'HI, WORLD!'`. The `upper()` method does not modify the original string but returns a new string with all characters in uppercase.

Answer

Hi, World!

Answer

Hello, World!

Answer

HELLO, WORLD!

Question 14

You are a developer at a company that processes customer feedback. Each feedback entry is stored as a string containing a rating (1-5) followed by a colon and then the comment. For example: '4: Great service'. You need to extract only the comments from feedback that have a rating of 4 or 5. You have a list of feedback strings. Which code snippet correctly implements this?

Accepted Answer

[s.split(':')[1].strip() for s in feedback if s.split(':')[0].strip() in ('4','5')]. It splits each feedback string on ':', extracts the comment (index [1]), strips whitespace, and filters only those entries where the rating (index [0], stripped) is exactly '4' or '5'. This ensures only comments from high-rated feedback are collected, handling potential spaces around the colon.

Answer

[s for s in feedback if s.startswith('4') or s.startswith('5')]

Answer

[s.split(':') for s in feedback][1]

Answer

[s.split(':')[1] for s in feedback if '4' in s or '5' in s]

Question 15

A developer needs to extract the file extension from a string like 'report.pdf'. Which string method is most appropriate?

Accepted Answer

str.split('.')[-1]. `str.split('.')[-1]` splits the string at each dot and returns the last element, which is the file extension. This method works reliably for simple cases like 'report.pdf' and is a common Python idiom for extracting extensions.

Answer

str.find('.')

Answer

str.partition('.')[2]

Answer

str.rstrip('.pdf')