7.4 Splitting and joining strings

split() method

• The string method split() splits a string into a list of tokens.
  • Each token is a substring that forms a part of a larger string.
• A separator is a character or sequence of characters that indicates where to split the string into tokens.
  • Ex: 'Martin Luther King Jr.'.split() splits the string literal "Martin Luther King Jr." using any whitespace character as the default separator and returns the list of tokens ['Martin', 'Luther', 'King', 'Jr.']
• The separator can be changed by calling split() with a string argument. Ex: 'a#b#c'.split('#') uses the "#" separator to split the string "a#b#c" into the three tokens ['a', 'b', 'c'].

join() method

• The join() string method performs the inverse operation of split() by joining a list of strings together to create a single string
  • Ex: my_str = '@'.join(['billgates', 'microsoft']) assigns my_str with the string 'billgates@microsoft'.
  • The separator '@' provides a join() method that accepts a single list argument

Using the split() and join() methods together

• The split() and join() methods are commonly used together to replace or remove specific sections of a string.
  • Ex: A programmer may want to change 'C:/Users/Brian/report.txt' to 'C:\Users\Brian\report.txt', perhaps because a different operating system uses different separators to specify file locations

• A programmer may also want to add, remove, or replace specific token(s) from a string.
  • Ex: The program below reads in a URL and checks whether the fourth token (index 3) is 'wiki', as Wikipedia URLs follow the format of http://language.wikipedia.org/wiki/topic.
  • If 'wiki' is missing from the URL, the program uses the list method insert() (explained further elsewhere) to correct the URL by adding 'wiki' before index 3.