Jul 9, 2023

Python - String Methods

Python’s built-in str class defines different methods. They help in manipulating strings. Since string is an immutable object, these methods return a copy of the original string, performing the respective processing on it. The string methods can be classified in following categories −

Case Conversion Methods

This category of built-in methods of Python’s str class deal with the conversion of alphabet characters in the string object. Following methods fall in this category −

Sr.No.	Method & Description
1	capitalize()Capitalizes first letter of string
2	casefold()Converts all uppercase letters in string to lowercase. Similar to lower(), but works on UNICODE characters alos
3	lower()Converts all uppercase letters in string to lowercase.
4	swapcase()Inverts case for all letters in string.
5	title()Returns “titlecased” version of string, that is, all words begin with uppercase and the rest are lowercase.
6	upper()Converts lowercase letters in string to uppercase.

Alignment Methods

Following methods in the str class control the alignment of characters within the string object.

Sr.No.	Methods & Description
1	center(width, fillchar)Returns a string padded with fillchar with the original string centered to a total of width columns.
2	[ljust(width, fillchar])Returns a space-padded string with the original string left-justified to a total of width columns.
3	[rjust(width,, fillchar])Returns a space-padded string with the original string right-justified to a total of width columns.
4	expandtabs(tabsize = 8)Expands tabs in string to multiple spaces; defaults to 8 spaces per tab if tabsize not provided.
5	zfill (width)Returns original string leftpadded with zeros to a total of width characters; intended for numbers, zfill() retains any sign given (less one zero).

Split and Join Methods

Python has the following methods to perform split and join operations −

Sr.No.	Method & Description
1	lstrip()Removes all leading whitespace in string.
2	rstrip()Removes all trailing whitespace of string.
3	strip()Performs both lstrip() and rstrip() on string
4	rsplit()Splits the string from the end and returns a list of substrings
5	split()Splits string according to delimiter (space if not provided) and returns list of substrings.
6	splitlines()Splits string at NEWLINEs and returns a list of each line with NEWLINEs removed.
7	partition()Splits the string in three string tuple at the first occurrence of separator
8	rpartition()Splits the string in three string tuple at the ladt occurrence of separator
9	join()Concatenates the string representations of elements in sequence into a string, with separator string.
10	removeprefix()Returns a string after removing the prefix string
11	removesuffix()Returns a string after removing the suffix string

Boolean String Methods

Following methods in str class return True or False.

Sr.No.	Methods & Description
1	isalnum()Returns true if string has at least 1 character and all characters are alphanumeric and false otherwise.
2	isalpha()Returns true if string has at least 1 character and all characters are alphabetic and false otherwise.
3	isdigit()Returns true if the string contains only digits and false otherwise.
4	islower()Returns true if string has at least 1 cased character and all cased characters are in lowercase and false otherwise.
5	isnumeric()Returns true if a unicode string contains only numeric characters and false otherwise.
6	isspace()Returns true if string contains only whitespace characters and false otherwise.
7	istitle()Returns true if string is properly “titlecased” and false otherwise.
8	isupper()Returns true if string has at least one cased character and all cased characters are in uppercase and false otherwise.
9	isascii()Returns True is all the characters in the string are from the ASCII character set
10	isdecimal()Checks if all the characters are decimal characters
11	isidentifier()Checks whether the string is a valid Python identifier
12	isprintable()Checks whether all the characters in the string are printable

Find and Replace Methods

Following are the Find and Replace methods in Python −

Sr.No.	Method & Description
1	count(sub, beg ,end)Counts how many times sub occurs in string or in a substring of string if starting index beg and ending index end are given.
2	find(sub, beg, end)Determine if sub occurs in string or in a substring of string if starting index beg and ending index end are given returns index if found and -1 otherwise.
3	index(sub, beg, end)Same as find(), but raises an exception if str not found.
4	[replace(old, new , max])Replaces all occurrences of old in string with new or at most max occurrences if max given.
5	rfind(sub, beg, end)Same as find(), but search backwards in string.
6	rindex( sub, beg, end)Same as index(), but search backwards in string.
7	startswith(sub, beg, end)Determines if string or a substring of string (if starting index beg and ending index end are given) starts with substring sub; returns true if so and false otherwise.
8	endswith(suffix, beg, end)Determines if string or a substring of string (if starting index beg and ending index end are given) ends with suffix; returns true if so and false otherwise.

Translation Methods

Following are the Translation methods of the string −

Sr.No.	Method & Description
1	maketrans()Returns a translation table to be used in translate function.
2	translate(table, deletechars="")Translates string according to translation table str(256 chars), removing those in the del string.

Sr.No.	Method & Description
1	capitalize()Capitalizes first letter of string
2	casefold()Converts all uppercase letters in string to lowercase. Similar to lower(), but works on UNICODE characters alos
3	lower()Converts all uppercase letters in string to lowercase.
4	swapcase()Inverts case for all letters in string.
5	title()Returns “titlecased” version of string, that is, all words begin with uppercase and the rest are lowercase.
6	upper()Converts lowercase letters in string to uppercase.

Sr.No.	Methods & Description
1	center(width, fillchar)Returns a string padded with fillchar with the original string centered to a total of width columns.
2	[ljust(width, fillchar])Returns a space-padded string with the original string left-justified to a total of width columns.
3	[rjust(width,, fillchar])Returns a space-padded string with the original string right-justified to a total of width columns.
4	expandtabs(tabsize = 8)Expands tabs in string to multiple spaces; defaults to 8 spaces per tab if tabsize not provided.
5	zfill (width)Returns original string leftpadded with zeros to a total of width characters; intended for numbers, zfill() retains any sign given (less one zero).

Sr.No.	Method & Description
1	lstrip()Removes all leading whitespace in string.
2	rstrip()Removes all trailing whitespace of string.
3	strip()Performs both lstrip() and rstrip() on string
4	rsplit()Splits the string from the end and returns a list of substrings
5	split()Splits string according to delimiter (space if not provided) and returns list of substrings.
6	splitlines()Splits string at NEWLINEs and returns a list of each line with NEWLINEs removed.
7	partition()Splits the string in three string tuple at the first occurrence of separator
8	rpartition()Splits the string in three string tuple at the ladt occurrence of separator
9	join()Concatenates the string representations of elements in sequence into a string, with separator string.
10	removeprefix()Returns a string after removing the prefix string
11	removesuffix()Returns a string after removing the suffix string

Sr.No.	Methods & Description
1	isalnum()Returns true if string has at least 1 character and all characters are alphanumeric and false otherwise.
2	isalpha()Returns true if string has at least 1 character and all characters are alphabetic and false otherwise.
3	isdigit()Returns true if the string contains only digits and false otherwise.
4	islower()Returns true if string has at least 1 cased character and all cased characters are in lowercase and false otherwise.
5	isnumeric()Returns true if a unicode string contains only numeric characters and false otherwise.
6	isspace()Returns true if string contains only whitespace characters and false otherwise.
7	istitle()Returns true if string is properly “titlecased” and false otherwise.
8	isupper()Returns true if string has at least one cased character and all cased characters are in uppercase and false otherwise.
9	isascii()Returns True is all the characters in the string are from the ASCII character set
10	isdecimal()Checks if all the characters are decimal characters
11	isidentifier()Checks whether the string is a valid Python identifier
12	isprintable()Checks whether all the characters in the string are printable

Sr.No.	Method & Description
1	count(sub, beg ,end)Counts how many times sub occurs in string or in a substring of string if starting index beg and ending index end are given.
2	find(sub, beg, end)Determine if sub occurs in string or in a substring of string if starting index beg and ending index end are given returns index if found and -1 otherwise.
3	index(sub, beg, end)Same as find(), but raises an exception if str not found.
4	[replace(old, new , max])Replaces all occurrences of old in string with new or at most max occurrences if max given.
5	rfind(sub, beg, end)Same as find(), but search backwards in string.
6	rindex( sub, beg, end)Same as index(), but search backwards in string.
7	startswith(sub, beg, end)Determines if string or a substring of string (if starting index beg and ending index end are given) starts with substring sub; returns true if so and false otherwise.
8	endswith(suffix, beg, end)Determines if string or a substring of string (if starting index beg and ending index end are given) ends with suffix; returns true if so and false otherwise.