如何遍历二维列表以打印表格？

Question

I have a class like this:

class example:
    def get_a(self): return [1,2,3]
    def get_b(self): return [4,5,6]
    def get_c(self): return [7,8,9]
    def get_all(self): return [['a',self.get_a()],['b',self.get_b()],['c',self.get_c()]]

And now I would like to use the return value of get_all to print a table like this:

a b c
1 4 7
2 5 8
3 6 9

I know I can get the same output via:

def example_print():
    x = example()
    print 'a b c'
    for a,b,c in zip(x.get_a(),x.get_b(),x.get_c()):
         print a,b,c 

But I am clueless on how to iterate the 2d list returned by get_all to print the same, especially as I am looking for a way that does not have the number of items hardcoded (want to use same way of printing the list for different instances that may have more "columns").

Answer 1

A simple way would be to use the zip transpose idiom, something like:

for x in zip(*e.get_all()):
    print(*x)

In Python 2, make sure you use:

from __future__ import print_function 

Or better yet, just switch to Python 3.

If your list actually has two levels of nesting. Which would require your method to be something like:

return  [['a',*self.get_a()],['b',*self.get_b()],['c',*self.get_c()]]

Or something equivalent in Python 2...

Answer 2

If you change your get_all definition to this:

def get_all(self): return ['a'] + self.get_a(), ['b'] + self.get_b(), ['c'] + self.get_c()

Then you'll be able to use something like this:

from __future__ import print_function

x = example()
for line in zip(*x.get_all()):
     print(*line)

Answer 3

I tried out this and it works.

class example:
    def get_a(self): return [1,2,3]
    def get_b(self): return [4,5,6]
    def get_c(self): return [7,8,9]


    def get_all(self):
        a = [['a', *self.get_a()], ['b', *self.get_b()], ['c', *self.get_c()]]
        r = []
        for line in zip(*a):
            r.append([*line])
        return r

if __name__ == '__main__':
    E = example()
    v = E.get_all()
    for i in v:
        print(*i)