PCAP Strings Practice Test 11 — 15 Questions

Question 1

Refer to the exhibit. Which of the following fixes the error?

Accepted Answer

Both A and B. Both A and B produce the string 'Hello5' without error. In Python, the + operator concatenates strings, so 'Hello' + '5' works. Option B converts the integer 5 to a string using str() before concatenation, which also works. Option D uses the * operator to repeat the string 'Hello' five times, producing 'HelloHelloHelloHelloHello', which is a valid operation but does not fix the error described in the exhibit (likely a TypeError from trying to concatenate a string and an integer).

Answer

print('Hello' + '5')

Answer

print('Hello' + str(5))

Answer

print('Hello' * 5)

Question 2

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 3

Which of the following is the BEST practice for building a large string by concatenating many smaller strings in Python?

Accepted Answer

result = ''.join(parts). `''.join(parts)` is the most efficient way to concatenate a large number of strings in Python. It allocates memory once for the final string by iterating over the list and copying each part into the result buffer, avoiding the O(n²) time complexity of repeated concatenation in a loop.

Answer

result = sum(parts, '')

Answer

result = str.concat(*parts)

Answer

result = ''; for part in parts: result += part

Question 4

A team is using f-strings to format a report. They have a variable `value = 0.123456789` and want to display it with exactly 3 significant digits. They write `f"{value:.3g}"`. The output is '0.123'. They expected '0.123'. Is the output correct? If not, what change would produce '0.123'?

Accepted Answer

The output is correct as is.. The format specifier `.3g` in an f-string instructs Python to format the number with 3 significant digits using general format. For `0.123456789`, the first three significant digits are '123', and the general format automatically switches to fixed-point notation when the exponent is small, producing '0.123' exactly as expected.

Answer

Use `f"{value:.3s}"`

Answer

Use `f"{value:.3f}"`

Answer

Use `f"{value:.3e}"`

Question 5

Which THREE of the following escape sequences are valid in a Python string and represent a single character? (Select exactly three.)

Accepted Answer

\'. The backslash followed by a single quote (\') is a valid escape sequence in Python that represents a literal single quote character, allowing it to appear inside a single-quoted string without terminating the string. This sequence is interpreted as a single character by the Python parser.

Answer

\x

Answer

\q

Question 6

Consider the following code:

print('"age": 30,')

Accepted Answer

"age": 30,. The code prints a literal string: "age": 30,. The double quotes are escaped within the single-quoted string, so they appear in the output. The trailing comma is part of the string, not a delimiter.

Answer

"age": 30

Answer

"name": "Alice",

Answer

"city": "New York"

Question 7

A developer writes code to display a floating-point number with exactly two decimal places. Which f-string expression is correct for value = 3.14159?

Accepted Answer

f"{value:.2f}". The format specifier `.2f` in an f-string explicitly instructs Python to format the floating-point number with exactly two digits after the decimal point. The `f` type ensures fixed-point notation, and the precision `.2` controls the number of decimal places. This is the standard way to achieve two-decimal-place output for a float in Python.

Answer

f"{value:0.2}"

Answer

f"{value:%2f}"

Answer

f"{value:2f}"

Question 8

Which of the following demonstrates that strings are immutable?

Accepted Answer

s[0] = 'J' results in a TypeError. Attempting to assign a new character to an index of a string (e.g., s[0] = 'J') raises a TypeError, which directly demonstrates that strings are immutable in Python. Immutability means the object's value cannot be changed after creation; any operation that appears to modify a string actually creates a new string object.

Answer

s.upper() changes s in place

Answer

s += '!' modifies s

Answer

s.replace('a','b') modifies s

Question 9

What is the result of 'abcdef'[::-2]?

Accepted Answer

'fdb'. The slicing syntax [::-2] means start from the end (default step negative), go to the beginning, and take every second character in reverse order. For 'abcdef', starting at 'f' (index -1), then skipping one to 'd' (index -3), then 'b' (index -5), resulting in 'fdb'. Option C is correct.

Answer

'dfb'

Answer

'ace'

Answer

'eca'

Question 10

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 11

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 12

A developer needs to combine a list of 10,000 strings into a single string. Which approach is most efficient in terms of memory and performance?

Accepted Answer

Use ''.join(string_list). The `''.join(string_list)` method is the most efficient because it pre-allocates memory for the final string by first calculating the total length of all strings in the list, then building the result in a single pass. This avoids the quadratic time complexity and repeated memory reallocations caused by string immutability in Python when using `+=` in a loop.

Answer

Use a loop with str += to concatenate each string

Answer

Use str.replace() to merge the strings

Answer

Use str.format() to build the string step by step

Question 13

A Python script reads a file containing text with non-ASCII characters like 'é' and 'ü'. The script must encode the string as UTF-8 then decode it back. Which of the following correctly handles this without error?

Accepted Answer

s.encode('utf-8').decode('utf-8'). It first encodes the string (which contains non-ASCII characters like 'é' and 'ü') into UTF-8 bytes using `.encode('utf-8')`, then decodes those bytes back into a string using `.decode('utf-8')`. This round-trip preserves all characters since UTF-8 can represent any Unicode code point, and the operations are applied in the correct order: a string is encoded to bytes, then bytes are decoded back to a string.

Answer

s.decode('utf-8').encode('utf-8')

Answer

s.encode('ascii').decode('ascii')

Answer

s.decode('utf-8').decode('utf-8')

Question 14

A QA engineer needs to verify that a user input string contains at least one uppercase letter, one lowercase letter, and one digit. Which regex pattern can be used with re.search() to achieve this?

Accepted Answer

r'(?=.*[A-Z])(?=.*[a-z])(?=.*\d)'. It uses lookahead assertions ((?=...)) to check for the presence of at least one uppercase letter, one lowercase letter, and one digit anywhere in the string, without consuming characters. This allows re.search() to return a match if all three conditions are met, regardless of order.

Answer

r'[A-Za-z0-9]'

Answer

r'([A-Z].*[a-z].*\d)|([a-z].*[A-Z].*\d)|...'

Answer

r'\d.*[a-z].*[A-Z]'

Question 15

A developer tries to modify a string: s = 'hello'; s[0] = 'H'. What happens when this code runs?

Accepted Answer

It raises a TypeError: 'str' object does not support item assignment. Strings in Python are immutable, meaning their contents cannot be changed after creation. Attempting to assign a new character to an index position (e.g., s[0] = 'H') raises a TypeError: 'str' object does not support item assignment. To modify a string, you must create a new string using slicing or concatenation.

Answer

It changes the string to 'Hello'

Answer

It creates a new string 'Hello' and assigns it to s

Answer

It raises an IndexError because index 0 is out of range