Python - String Methods

A method is a function that belongs to an object.

In Python, every string has a built-in set of methods that we can call using dot notation: text.method(arguments)

Important: String methods never modify the original string. They return a new string, because strings are immutable.

upper() converts all characters to uppercase, and lower() converts all characters to lowercase.

title() capitalizes the first letter of every word, while capitalize() capitalizes only the first letter of the string.

swapcase() converts uppercase letters to lowercase and lowercase letters to uppercase.

isupper() returns True if all characters are uppercase. islower() returns True if all characters are lowercase.

istitle() returns True if every word starts with an uppercase letter.

isalpha() returns True if the string contains only letters. isdigit() returns True if the string contains only digits.

isalnum() returns True if the string contains only letters and digits (no spaces or symbols).

isspace() returns True if the string contains only whitespace characters.

strip() removes leading and trailing spaces from a string.

lstrip() removes only the left (leading) spaces, and rstrip() removes only the right (trailing) spaces.

We can pass characters to strip() to remove them from both ends of the string.

find() returns the index of the first occurrence of a substring. rfind() returns the index of the last occurrence.

If the substring is not found, find() returns -1.

index() and rindex() work like find() and rfind(), but they raise a ValueError if the substring is not found.

count() returns how many times a substring appears in the string.

replace() replaces all occurrences of a substring with another substring. A third argument limits how many replacements are made.

split() divides a string into a list of words. By default, it splits on spaces.

We can pass a separator and a maximum number of splits.

splitlines() splits a multi-line string into a list of lines.

join() is the opposite of split(). It joins a list of strings into one string using a separator.

startswith() checks whether the string begins with a given substring. endswith() checks whether it ends with a given substring.

These methods pad the string to a given width. center() places the string in the middle, ljust() on the left, and rjust() on the right.

zfill() pads the string with zeros on the left until it reaches the given width.

Using slicing, we can reverse a string in one line.

Split the sentence into words, reverse the list, and join it back.

Loop through the string and count every vowel using the in operator.

A palindrome reads the same forwards and backwards.