Python之String Methods

Here are some of the most common string methods. A method is like a function, but it runs "on" an object. If the variable s is a string, then the code s.lower() runs the lower() method on that string object and returns the result (this idea of a method running on an object is one of the basic ideas that make up Object Oriented Programming, OOP). Here are some of the most common string methods:

• s.lower(), s.upper() -- returns the lowercase or uppercase version of the string
• s.strip() -- returns a string with whitespace removed from the start and end
• s.isalpha()/s.isdigit()/s.isspace()... -- tests if all the string chars are in the various character classes
• s.startswith('other'), s.endswith('other') -- tests if the string starts or ends with the given other string
• s.find('other') -- searches for the given other string (not a regular expression) within s, and returns the first index where it begins or -1 if not found
• s.replace('old', 'new') -- returns a string where all occurrences of 'old' have been replaced by 'new'
• s.split('delim') -- returns a list of substrings separated by the given delimiter. The delimiter is not a regular expression, it's just text. 'aaa,bbb,ccc'.split(',') -> ['aaa', 'bbb', 'ccc']. As a convenient special case s.split() (with no arguments) splits on all whitespace chars.
• s.join(list) -- opposite of split(), joins the elements in the given list together using the string as the delimiter. e.g. '---'.join(['aaa', 'bbb', 'ccc']) -> aaa---bbb---ccc