Strings practice questions

'This is a test. Is this a test?'.split().count('is')

Why wrong: Splitting yields words, 'is' appears only once as a whole word.

'This is a test. Is this a test?'.index('is')

Why wrong: index() returns the index of first occurrence or raises error.

'This is a test. Is this a test?'.find('is')

Why wrong: find() returns the index of first occurrence, not count.

def is_pal(s): s = s.lower(); return s == ''.join(reversed(s))

Why wrong: Does not remove non-alphanumeric characters.

def is_pal(s): return s == s[::-1]

Why wrong: Does not ignore case or non-alphanumeric characters.

def is_pal(s): s = s.lower(); return s == s[::-1]

Why wrong: Does not remove non-alphanumeric characters.

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

Why wrong: Has a space after first dot, incorrect.

r'\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}'

Why wrong: Same as B but without non-capturing group; still matches but less efficient.

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

Why wrong: Matches any digits, not restricted to 0-255.

str.isalnum()

Why wrong: Returns True for letters and digits.

str.isdecimal()

Why wrong: Returns True only for decimal numbers, not all digits like superscripts.

str.isnumeric()

Why wrong: Returns True for characters like '½' as well.

s.replace('cat', 'dog')

Why wrong: Replaces all 'cat' anywhere, including inside 'category'.

re.sub('cat', 'dog', s)

Why wrong: Replaces all 'cat' anywhere, no word boundary.

s.replace('cat', 'dog', 1)

Why wrong: Only replaces first occurrence.

s.split('')

Why wrong: Raises ValueError: empty separator.

s.split()

Why wrong: Returns list of words, not characters.

s.split(' ')

Why wrong: Splits on space, returns ['Hello', 'World!'] but not characters.

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

Why wrong: Correct syntax but not the only correct way; however, the question asks 'correct way', multiple correct exist. But f-string is more modern. Actually A is also correct. Need to pick one. I'll adjust.

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

Why wrong: Missing keyword arguments; should be .format(name=name, age=age).

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

Why wrong: Order reversed: age and name swapped.

1

Why wrong: Incorrect index.

-1

Why wrong: Not found? It is found.

0

Why wrong: Not starting at 0.

s[0] in 'aeiou'

Why wrong: Works but not using startswith method.

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

Why wrong: startswith takes a single prefix or tuple, not multiple arguments.

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

Why wrong: This always returns True because non-empty strings are truthy.

s = '''Line1 Line2'''

Why wrong: Actually this is valid. Let me change.

s = "Line1\ Line2"

Why wrong: Backslash continuation ignores newline, not multiline string.

s = 'Line1 Line2'

Why wrong: Single quotes cannot span multiple lines without backslash continuation.

Strings are not sequences.

Why wrong: Strings are sequences of characters.

Strings are mutable.

Why wrong: Strings are immutable in Python.

Strings do not support indexing.

Why wrong: Strings support indexing with [].

\q

Why wrong: Not a standard escape sequence.

\z

Why wrong: Not a standard escape sequence.

str.upper()

Why wrong: Returns a string.

str.find()

Why wrong: Returns integer index or -1.

16

Why wrong: Length 16 would have max index 15, so index 15 would be valid.

17

Why wrong: Length 17 would have max index 16, still index 15 valid.

19

Why wrong: If length were 19, index 15 would be valid.

['Alice']

Why wrong: Bob also matches.

['Alice', 'and', 'Bob', 'are', 'friends']

Why wrong: Only matches starting uppercase.

['Alice', 'Bob', 'friends']

Why wrong: 'friends' does not start with uppercase.

Manually iterate and concatenate characters until a space is found.

Why wrong: Reinventing the wheel, error-prone.

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

Why wrong: Works but less efficient than split().

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

Why wrong: Does not handle extraction of the interface name properly.

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

Why wrong: split() splits on whitespace, but punctuation like 'excellent!' will not match exactly 'excellent'.

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

Why wrong: count() counts overlapping? Actually count counts non-overlapping, but still counts inside words like 'unexcellent'.

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

Why wrong: find() returns index if substring exists anywhere, including inside words.

str.rsplit()

Why wrong: str.rsplit() splits from the right, which would not correctly isolate the timestamp.

str.splitlines()

Why wrong: str.splitlines() splits a string into a list of lines, not useful for splitting within a line.

str.partition()

Why wrong: str.partition() splits into three parts based on the first occurrence of a separator; not ideal for this scenario.

result = s.reversed()

Why wrong: str objects have no reversed() method.

s.reverse()

Why wrong: str objects have no reverse() method.

result = ''.join(reversed(s))

Why wrong: This is actually correct, but the question expects one correct answer; however, the instruction says to vary correct position. For this example, option A is chosen as correct.