# Introduction The `str` class offers [many useful methods][str methods] for working with and composing strings. These include searching, cleaning, splitting, transforming, translating, and many other techniques. Strings are [sequences][text sequence] of [Unicode code points][unicode code points] -- individual "characters" or code points (_strings of length 1_) can be referenced by `0-based index` number from the left, or `-1-based index` number from the right. Strings implement all [common sequence operations][common sequence operations]. They can be iterated through using `for item in ` or `for index, item in enumerate()` syntax. They can also be concatenated using ` + ` or `.join()`. Strings are _immutable_, meaning the value of a `str` object in memory cannot change. Functions or methods that operate on a `str` (_like the ones we are learning about here_) will return a new `instance` of that `str` object instead of modifying the original `str`. Following is a small selection of Python string methods. For a complete list, see the [str class][str methods] in the Python docs. [`.title()`][str-title] parses a string and capitalizes the first "character" of each "word" found. In Python, this is very dependent on the [language codec][codecs] used and how the particular language represents words and characters. There may also be [locale][locale] rules in place for a language or character set. ```python man_in_hat_th = 'ผู้ชายใส่หมวก' man_in_hat_ru = 'мужчина в шляпе' man_in_hat_ko = '모자를 쓴 남자' man_in_hat_en = 'the man in the hat.' >>> man_in_hat_th.title() 'ผู้ชายใส่หมวก' >>> man_in_hat_ru.title() 'Мужчина В Шляпе' >>> man_in_hat_ko.title() '모자를 쓴 남자' >> man_in_hat_en.title() 'The Man In The Hat.' ``` [`.endswith()`][str-endswith] returns `True` if the string ends with ``, `False` otherwise. ```python >>> 'My heart breaks. 💔'.endswith('💔') True >>> 'cheerfulness'.endswith('ness') True # Punctuation is part of the string, so needs to be included in any endswith match. >>> 'Do you want to 💃?'.endswith('💃') False >> 'The quick brown fox jumped over the lazy dog.'.endswith('dog') False ``` [`.strip()`][str-strip] returns a copy of the `str` with leading and trailing `` removed. The code points specified in `` are not a prefix or suffix - **all combinations** of the code points will be removed starting from **both ends** of the string. If nothing is specified for ``, all combinations of whitespace code points will be removed. ```python # This will remove "https://", because it can be formed from "/stph:". >>> 'https://unicode.org/emoji/'.strip('/stph:') 'unicode.org/emoji' # Removal of all whitespace from both ends of the str. >>> ' 🐪🐪🐪🌟🐪🐪🐪 '.strip() '🐪🐪🐪🌟🐪🐪🐪' >>> justification = 'оправдание' >>> justification.strip('еина') 'оправд' # Prefix and suffix in one step. >>> 'unaddressed'.strip('dnue') 'address' >>> ' unaddressed '.strip('dnue ') 'address' ``` [`.replace(, )`][str-replace] returns a copy of the string with all occurrences of `` replaced with ``. The quote used below is from [The Hunting of the Snark][The Hunting of the Snark] by [Lewis Carroll][Lewis Carroll] ```python # The Hunting of the Snark, by Lewis Carroll >>> quote = ''' "Just the place for a Snark!" the Bellman cried, As he landed his crew with care; Supporting each man on the top of the tide By a finger entwined in his hair. "Just the place for a Snark! I have said it twice: That alone should encourage the crew. Just the place for a Snark! I have said it thrice: What I tell you three times is true." ''' >>> quote.replace('Snark', '🐲') ... '\n"Just the place for a 🐲!" the Bellman cried,\n As he landed his crew with care;\nSupporting each man on the top of the tide\n By a finger entwined in his hair.\n\n"Just the place for a 🐲! I have said it twice:\n That alone should encourage the crew.\nJust the place for a 🐲! I have said it thrice:\n What I tell you three times is true."\n' >>> 'bookkeeper'.replace('kk', 'k k') 'book keeper' ``` [Lewis Carroll]: https://www.poetryfoundation.org/poets/lewis-carroll [The Hunting of the Snark]: https://www.poetryfoundation.org/poems/43909/the-hunting-of-the-snark [codecs]: https://docs.python.org/3/library/codecs.html [common sequence operations]: https://docs.python.org/3/library/stdtypes.html#text-sequence-type-str [locale]: https://docs.python.org/3/library/locale.html#module-locale [str methods]: https://docs.python.org/3/library/stdtypes.html#string-methods [str-endswith]: https://docs.python.org/3/library/stdtypes.html#str.endswith [str-replace]: https://docs.python.org/3/library/stdtypes.html#str.replace [str-strip]: https://docs.python.org/3/library/stdtypes.html#str.strip [str-title]: https://docs.python.org/3/library/stdtypes.html#str.title [text sequence]: https://docs.python.org/3/library/stdtypes.html#text-sequence-type-str [unicode code points]: https://stackoverflow.com/questions/27331819/whats-the-difference-between-a-character-a-code-point-a-glyph-and-a-grapheme