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
