在python中打印列表输出的最佳方法

Question

I have a list and a list of list like this

>>> list2 = [["1","2","3","4"],["5","6","7","8"],["9","10","11","12"]]
>>> list1 = ["a","b","c"]

I zipped the above two list so that i can match their value index by index.

>>> mylist = zip(list1,list2)
>>> mylist
[('a', ['1', '2', '3', '4']), ('b', ['5', '6', '7', '8']), ('c', ['9', '10', '11', '12'])]

Now I tried to print the output of above mylist using

>>> for item in mylist:
...     print item[0]
...     print "---".join(item[1])
...

It resulted in this output which is my desired output .

a
1---2---3---4
b
5---6---7---8
c
9---10---11---12

Now, my question is there a more cleaner and better way to achieve my desired output or this is the best(short and more readable) possible way.

Answer 1

Well, you could avoid some temporary variables and use a nicer loop:

for label, vals in zip(list1, list2):
    print label
    print '---'.join(vals)

I don't think you're going to get anything fundamentally "better," though.

Answer 2

The following for loop will combine both the print and join operations into one line.

 for item in zip(list1,list2):
     print '{0}\n{1}'.format(item[0],'---'.join(item[1]))

Answer 3

It may not be quite as readable as a full loop solution, but the following is still readable and shorter:

>>> zipped = zip(list1, list2) 
>>> print '\n'.join(label + '\n' + '---'.join(vals) for label, vals in zipped)
a
1---2---3---4
b
5---6---7---8
c
9---10---11---12

Answer 4

Here's another way to achieve the result. It's shorter, but I'm not sure it's more readable:

print '\n'.join([x1 + '\n' + '---'.join(x2) for x1,x2 in zip(list1,list2)])

Answer 5

What you might consider clean, but I do not, is that your the rest of your program needs to now the structure of your data and how to print it. IMHO that should be contained in the class of the data, so you can just do print mylist and get the desired result.

If you combine that with mgilson's suggestion to use a dictionary ( I would even suggest an OrderedDict) I would do something like this:

from collections import OrderedDict

class MyList(list):
    def __init__(self, *args):
        list.__init__(self, list(args))

    def __str__(self):
        return '---'.join(self)

class MyDict(OrderedDict):
    def __str__(self):
        ret_val = []
        for k, v in self.iteritems():
            ret_val.extend((k, str(v)))
        return '\n'.join(ret_val)

mydata = MyDict([
    ('a', MyList("1","2","3","4")),
    ('b', MyList("5","6","7","8")),
    ('c', MyList("9","10","11","12")),
])

print mydata

without requiring the rest of the program needing to know the details of printing this data.