Tuples

A tuple is an immutable list. Immutable means that it cannot be modified. A tuple is just a comma-separated sequence of objects (a list without brackets). To increase readability, one often encloses a tuple in a pair of parentheses:

my_tuple = 1, 2, 3     # our first tuple
my_tuple = (1, 2, 3)   # the same
my_tuple = 1, 2, 3,    # again the same
len(my_tuple) # 3, same as for lists
my_tuple[0] = 'a'   # error! tuples are immutable

The comma indicates that the object is a tuple:

singleton = 1,   # note the comma
len(singleton)   # 1

Tuples are useful when a group of values goes together; for example, they are used to return multiple values from functions (refer to section Returns Values in Chapter 7, Functions. One may assign several variables at once by unpacking a list or tuple:

a, b = 0, 1 # a gets 0 and b gets 1
a, b = [0, 1] # exactly the same effect
(a, b) = 0, 1 # same
[a,b] = [0,1] # same thing