PCAP Strings Practice Test 2 — 15 Questions

Question 1

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 2

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 3

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 4

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 5

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 6

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 7

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')

Question 8

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 9

Drag and drop the steps to debug a Python script using pdb into the correct order.

Accepted Answer

Step 1: Start the pdb debugger. Step 2: Run the script. Step 3: Step through the code. Step 4: Inspect variables. Step 5: Exit the debugger.. Debugging with pdb involves setting a trace, running the script, using commands to step through code, setting breakpoints, and exiting.

Answer

Step 1: Start the pdb debugger. Step 2: Inspect variables. Step 3: Step through the code. Step 4: Run the script. Step 5: Exit the debugger.

Answer

Step 1: Run the script. Step 2: Start the pdb debugger. Step 3: Step through the code. Step 4: Inspect variables. Step 5: Exit the debugger.

Answer

Step 1: Start the pdb debugger. Step 2: Step through the code. Step 3: Run the script. Step 4: Inspect variables. Step 5: Exit the debugger.

Question 10

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 11

Match each string method to its purpose.

Accepted Answer

upper(): Converts all characters to uppercase.. The correct matches are: .upper() converts to uppercase, .lower() converts to lowercase, .strip() removes leading/trailing whitespace. Common confusions include swapping .split() and .replace(), and confusing .replace() with .upper().

Answer

split(): Replaces all occurrences of a substring with another.

Answer

join(): Splits the string into a list of substrings.

Answer

replace(): Converts all characters to uppercase.

Question 12

Match each variable scope to its description.

Accepted Answer

Local: Variables defined inside a function.. The LEGB rule defines scope lookup order: Local, Enclosing, Global, Built-in. Correct matches are Local (inside function), Enclosing (outer function), Global (module level). Built-in consists of Python's predefined names.

Answer

Built-in: Variables defined at the top level of a module.

Answer

Local: Variables defined in an enclosing function.

Answer

Global: Predefined names like print and len.

Question 13

Which of the following expressions returns the string 'Hello' repeated three times?

Accepted Answer

'Hello' * 3. In Python, the multiplication operator (*) when used with a string and an integer performs string repetition. 'Hello' * 3 returns the string 'HelloHelloHello' by concatenating three copies of the original string. This is a core feature of Python's sequence protocol, where strings are sequences of characters.

Answer

'Hello' + 3

Answer

'Hello' * '3'

Answer

'Hello' * 3.0

Question 14

What is the result of the expression 'aBc'.lower()?

Accepted Answer

'abc'. The `lower()` method returns a new string with all cased characters converted to lowercase. Since the original string 'aBc' contains an uppercase 'B', calling `.lower()` converts it to 'b', resulting in 'abc'. The method does not modify the original string but returns a new one.

Answer

'Abc'

Answer

'aBc'

Answer

'ABC'

Question 15

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)