Python tuples sorting based on last element [duplicate]

问题

This question already has answers here:

Tuple pairs, finding minimum using python (3 answers)

Closed 6 years ago.

Here is my question i have tuple1=[(1, 3), (3, 2), (2, 1)] i want to sort tuple based on last digit of each tuple so the resultant will look like this output=[(2, 1), (3, 2), (1, 3)] below is my code

    i=0
for x in tuples:
    c.append(x[len(x)-1])
    last=sorted(c)
    for y in last.iteritems():
        if(y in x[len(x)-1]):
            print x             
            #b.insert(i,x)
i=i+1

after running iam getting an error message

    Traceback (most recent call last):
    File "x.py", line 47, in <module>
   sort_last([(1, 3), (3, 2), (2, 1)])
  File "x.py", line 35, in sort_last
 if(y in x[len(x)-1]):
  TypeError: argument of type 'int' is not iterable

回答1:

Specify the key argument in the sorted function.

>>> tuple1=[(1, 3), (3, 2), (2, 1)]
>>> output = sorted(tuple1, key=lambda x: x[-1])
>>> print output
[(2, 1), (3, 2), (1, 3)]

The sorted function (as well as the list.sort method) has an optional key argument which specifies what to sort the list on.

来源：https://stackoverflow.com/questions/14829300/python-tuples-sorting-based-on-last-element