PCEP-30-02 3.4 working with strings.txt

#SECTION: PCEP-30-02 3.4 Working with Strings in Python

==QUESTION 1==
Which of the following is a valid way to create a string in Python?
[A] str = 'Hello'
[B] str = "Hello"
[C] str = '''Hello'''
[D] All of the above
CORRECT: D
EXPLANATION: In Python, strings can be created using single quotes, double quotes, or triple quotes. All of these methods are valid and equivalent.

==QUESTION 2==
What is the output of the following code?
```python
s = "Python"
print(s[1])
```
[A] P
[B] y
[C] t
[D] h
CORRECT: B
EXPLANATION: String indexing in Python starts at 0. So s[1] refers to the second character of the string, which is 'y'.

==QUESTION 3==
What is string slicing?
[A] Removing characters from a string
[B] Adding characters to a string
[C] Extracting a portion of a string
[D] Replacing characters in a string
CORRECT: C
EXPLANATION: String slicing is a way to extract a portion of a string by specifying a range of indices.

==QUESTION 4==
Which of the following is true about strings in Python?
[A] Strings are mutable
[B] Strings are immutable
[C] Strings can be changed in-place
[D] None of the above
CORRECT: B
EXPLANATION: Strings in Python are immutable, meaning once a string is created, it cannot be changed.

==QUESTION 5==
How do you escape a single quote in a string that's enclosed in single quotes?
[A] \'
[B] "'"
[C] \\'
[D] Both A and B
CORRECT: D
EXPLANATION: You can escape a single quote using a backslash (\') or by enclosing it in double quotes ("'"). Both methods work.

==QUESTION 6==
What is the output of this code?
```python
print("He said, \"Hello!\"")
```
[A] He said, "Hello!"
[B] He said, \"Hello!\"
[C] "He said, "Hello!""
[D] SyntaxError
CORRECT: A
EXPLANATION: The backslashes are used to escape the double quotes, allowing them to be printed as part of the string.

==QUESTION 7==
How can you create a multi-line string?
[A] Using triple quotes (''' or """)
[B] Using \n in a regular string
[C] Using the + operator to concatenate strings
[D] All of the above
CORRECT: D
EXPLANATION: Multi-line strings can be created using triple quotes, newline characters (\n), or by concatenating multiple strings.

==QUESTION 8==
What is the output of this code?
```python
s = "Hello\nWorld"
print(len(s))
```
[A] 10
[B] 11
[C] 12
[D] Error
CORRECT: B
EXPLANATION: The string contains 10 visible characters plus one newline character (\n), totaling 11 characters.

==QUESTION 9==
Which method converts a string to uppercase?
[A] s.upper()
[B] s.capitalize()
[C] s.top()
[D] s.uppercase()
CORRECT: A
EXPLANATION: The upper() method is used to convert a string to uppercase in Python.

==QUESTION 10==
What is the output of this code?
```python
s = "  Hello, World!  "
print(s.strip())
```
[A] "Hello, World!"
[B] "Hello,World!"
[C] "  Hello, World!  "
[D] "Hello, World!  "
CORRECT: A
EXPLANATION: The strip() method removes leading and trailing whitespace from a string.

==QUESTION 11==
How do you check if a string starts with a specific substring?
[A] s.startswith("sub")
[B] s.begins("sub")
[C] s.start("sub")
[D] "sub" in s[0]
CORRECT: A
EXPLANATION: The startswith() method is used to check if a string starts with a specific substring.

==QUESTION 12==
What is the output of this code?
```python
s = "Python"
print(s[-2])
```
[A] P
[B] n
[C] o
[D] t
CORRECT: C
EXPLANATION: Negative indexing in Python counts from the end of the string. s[-2] refers to the second-to-last character, which is 'o'.

==QUESTION 13==
Which method splits a string into a list of substrings?
[A] s.split()
[B] s.divide()
[C] s.separate()
[D] s.break()
CORRECT: A
EXPLANATION: The split() method is used to split a string into a list of substrings based on a delimiter.

==QUESTION 14==
What is the output of this code?
```python
s = "Hello" + " " + "World"
print(s)
```
[A] HelloWorld
[B] Hello World
[C] "Hello World"
[D] Error
CORRECT: B
EXPLANATION: The + operator concatenates strings. The result is "Hello World" with a space between the words.

==QUESTION 15==
How can you find the index of a substring in a string?
[A] s.find("sub")
[B] s.index("sub")
[C] s.search("sub")
[D] Both A and B
CORRECT: D
EXPLANATION: Both find() and index() methods can be used to find the index of a substring in a string.

==QUESTION 16==
What is the output of this code?
```python
s = "Python"
print(s[1:4])
```
[A] Pyt
[B] yth
[C] ytho
[D] ython
CORRECT: B
EXPLANATION: String slicing s[1:4] includes characters from index 1 to 3 (4 is exclusive), which are 'yth'.

==QUESTION 17==
Which method replaces occurrences of a substring in a string?
[A] s.replace("old", "new")
[B] s.swap("old", "new")
[C] s.change("old", "new")
[D] s.substitute("old", "new")
CORRECT: A
EXPLANATION: The replace() method is used to replace occurrences of a substring in a string.

==QUESTION 18==
What is the output of this code?
```python
s = "Hello"
print(s * 3)
```
[A] HelloHelloHello
[B] Hello3
[C] Error
[D] None of the above
CORRECT: A
EXPLANATION: The * operator with a string repeats the string that many times.

==QUESTION 19==
How do you convert a string to lowercase?
[A] s.lower()
[B] s.lowercase()
[C] s.down()
[D] s.tolower()
CORRECT: A
EXPLANATION: The lower() method is used to convert a string to lowercase in Python.

==QUESTION 20==
What is the output of this code?
```python
s = "Python Programming"
print(s.count("P"))
```
[A] 1
[B] 2
[C] 3
[D] 0
CORRECT: B
EXPLANATION: The count() method returns the number of occurrences of a substring in the string. There are two "P"s in "Python Programming".

==QUESTION 21==
Which of the following is true about string formatting in Python?
[A] It can be done using the % operator
[B] It can be done using the .format() method
[C] It can be done using f-strings (in Python 3.6+)
[D] All of the above
CORRECT: D
EXPLANATION: Python supports multiple ways of string formatting, including the % operator, .format() method, and f-strings in newer versions.

==QUESTION 22==
What is the output of this code?
```python
s = "Hello\tWorld"
print(len(s))
```
[A] 10
[B] 11
[C] 12
[D] Error
CORRECT: B
EXPLANATION: The string contains 10 visible characters plus one tab character (\t), totaling 11 characters.

==QUESTION 23==
How can you check if a string contains only digits?
[A] s.isdigit()
[B] s.isnumeric()
[C] s.isdecimal()
[D] All of the above
CORRECT: D
EXPLANATION: All these methods (isdigit(), isnumeric(), and isdecimal()) can be used to check if a string contains only digits, with slight differences in what they consider as digits.

==QUESTION 24==
What is the output of this code?
```python
s = "Python"
print(s[::-1])
```
[A] Python
[B] nohtyP
[C] Pytho
[D] Error
CORRECT: B
EXPLANATION: The slice s[::-1] reverses the string, resulting in "nohtyP".

==QUESTION 25==
Which method joins elements of an iterable into a string?
[A] "".join(iterable)
[B] string.concat(iterable)
[C] string.merge(iterable)
[D] "".combine(iterable)
CORRECT: A
EXPLANATION: The join() method is used to join elements of an iterable into a string, with the string it's called on as the separator.