Star expressions

They are useful when iterating over a sequence of tuples of varying lengths.

Also, they are useful when combined with certain kinds of string processing operations, such as splitting.

line = 'nobody:*:-2:-2:Unprivileged User:/var/empty:/usr/bin/false'

uname, *fields, homedir, sh = line.split(':')

Examples

• You want to drop the first and last grades and return the average of the remaining grades:

  def drop_first_last(grades):
    first, *middle, last = grades
    return avg(middle)
  

• You have a single name and email, but an arbitrary number of phone numbers.

  name, email, *phone_numbers = ('Dave', '[email protected]', '2312', '32121')
  # phone_numbers = ['2312', '32121']
  

  Here phone_numbers will be always a list, regardless of the number of numbers including None.

• name, *_, (*_, year) = ('ACME', 50, 123.45, (12, 18, 2012))
  # name = 'ACME', year=2012