I'm following a couple of Pythone exercises and I'm stumped at this one.
# C. sort_last
# Given a list of non-empty tuples, return a list sorted in increasing
# order by the last element in each tuple.
# e.g. [(1, 7), (1, 3), (3, 4, 5), (2, 2)] yields
# [(2, 2), (1, 3), (3, 4, 5), (1, 7)]
# Hint: use a custom key= function to extract the last element form each tuple.
def sort_last(tuples):
# +++your code here+++
return
What is a Tuple? Do they mean a List of Lists?
The tuple is the simplest of Python's sequence types. You can think about it as an immutable (read-only) list:
>>> t = (1, 2, 3)
>>> print t[0]
1
>>> t[0] = 2
TypeError: tuple object does not support item assignment
Tuples can be turned into new lists by just passing them to list() (like any iterable), and any iterable can be turned into a new tuple by passing it to tuple():
>>> list(t)
[1, 2, 3]
>>> tuple(["hello", []])
("hello", [])
Hope this helps. Also see what the tutorial has to say about tuples.
A tuple and a list is very similar. The main difference (as a user) is that a tuple is immutable (can't be modified)
In your example:
[(2, 2), (1, 3), (3, 4, 5), (1, 7)]
This is a list of tuples [...] is the list (2,2) is a tuple
Tuples are used to group related variables together. It's often more convenient to use a tuple rather than writing yet another single-use class. Granted, accessing their content by index is more obscure than a named member variable, but it's always possible to use 'tuple unpacking':
def returnTuple(a, b):
return (a, b)
a, b = returnTuple(1, 2)
The best summary of the differences between lists and tuples I have read is this:
One common summary of these more interesting, if subtle, differences is that tuples are heterogeneous and lists are homogeneous. In other words: Tuples (generally) are sequences of different kinds of stuff, and you deal with the tuple as a coherent unit. Lists (generally) are sequences of the same kind of stuff, and you deal with the items individually.