Courses AQA GCSE Computer Science Python Coding Strings Methods & String Manipulation

Strings Methods & String Manipulation

len()

The len(object) function returns the number of characters in a string.

str = "Hello, world!"
length = len(str)  # Output: 13

The length of a string can be determined using the [[len]] function.

{"cloze_text": "The length of a string can be determined using the [[len]] function."}

upper(), lower() and title()

Uppercase

The upper() method converts all characters in a string to uppercase. You can also use the lower() and title() methods.

str = "hello"
uppercaseStr = str.upper()  # Output: "HELLO"

Lowercase

The lower() method converts all characters in a string to lowercase.

str = "hello"
lowercaseStr = str.lower()  # Output: "hello"

Title case

The title() method capitalizes the first letter of each word in a string.

str = "hello"
titlecaseStr = str.title()  # Output: "Hello"

The [[upper]] method converts all characters in a string to uppercase.

{"cloze_text": "The [[upper]] method converts all characters in a string to uppercase."}

replace()

The replace(original,replacement) method replaces a specified character or substring with another.

str = "Hello, world!"
newStr = str.replace("world", "John")  # Output: "Hello, John!"

Note: the replace method does not alter the original string, rather it returns a new string

In Python, which statement about the string 'replace' method is true?

{"answers": {"A": "It can only replace substrings of the same length", "B": "It only replaces the first occurrence of the specified substring", "C": "It returns a new string with replacements made", "D": "It modifies the original string in place"}, "question_text": "In Python, which statement about the string 'replace' method is true?", "correct_answer": "C"}

split()

The split(delimiter) method splits a string into an array of substrings based on a specified separator.

str = "Hello, world!"
parts = str.split(", ")  # Output: ["Hello", "world!"]

These string methods provide powerful tools for working with text data and enable you to perform various manipulations and transformations on strings

The [[split]] method splits a string into a list of substrings based on a specified delimiter.

{"cloze_text": "The [[split]] method splits a string into a list of substrings based on a specified delimiter."}

Searching and Extracting Substrings

index()

The `index()` method returns the index of the first occurrence of a specified substring within a string.
It can be used to determine whether a substring exists in a string and find its position if it does.
If the substring is not found, `index()` returns -1.

text = "Hello, world!"
index = text.index("world")  # Output: 7

rfind()

Similar to `index()`, the `rfind()` method returns the index of the last occurrence of a specified substring within a string.

It can be used to find the last position of a substring within a string.

text = "Hello, world!"
last_index = text.rfind("o")  # Output: 8

The [[index]] method returns the index of the first occurrence of a specified substring.

{"cloze_text": "The [[index]] method returns the index of the first occurrence of a specified substring."}

String slicing [stard:end]

You can extract a substring from a string using square brackets. The extracted substring includes the character at the starting index but excludes the character at the ending index.

text = "MOUSE"
substring = text[1:5]  # Output: "OUSE"

String slicing allows you to extract a [[substring]] from a larger string.

{"cloze_text": "String slicing allows you to extract a [[substring]] from a larger string."}

Negative Slicing

Negative slicing in Python allows you to specify indices relative to the end of the string.

text = "MOUSE"
substring = text[-4:-1]  # Output: "OUS"

Negative indices can be used in string slicing to start counting from the [[end]] of the string.

{"cloze_text": "Negative indices can be used in string slicing to start counting from the [[end]] of the string."}

.join()

In Python, the join() method is used to concatenate elements of an iterable, such as a list, tuple, or string, into a single string.

my_list = ["apple", "banana", "cherry"]
result = ", ".join(my_list)
print(result)  # Output: "apple, banana, cherry"

If the iterable contains non-string elements, you need to convert them to strings before using join().

numbers = [1, 2, 3, 4, 5]
result = "-".join(str(num) for num in numbers)
print(result)  # Output: "1-2-3-4-5"

What does the join() method do in Python?

{"answers": {"A": "Removes whitespace from the beginning and end of a string", "B": "Splits a string into a list based on a delimiter", "C": "Reverses the characters in a string", "D": "Concatenates elements of an iterable into a single string using a specified separator"}, "question_text": "What does the join() method do in Python?", "correct_answer": "D"}

Review: Fill in the Blanks

The function is used to determine the number of in a string. For example, if the string is "Hello, world!", the length returned by len() would be .

The method transforms all characters in a string to . Conversely, the method changes all characters to , while the method capitalizes the first letter of each in a string.

The method allows for the substitution of a specified character or substring with another, returning a new string without altering the original. For instance, using replace() to change "world" to "John" in "Hello, world!" results in the new string .

The method divides a string into an array of substrings based on a designated . Additionally, the method identifies the index of the first occurrence of a specified substring, whereas returns the index of the last occurrence. For example, if the text is "Hello, world!", the index of "world" is .

Click the keywords below to fill in the blanks: