Pythonic way to print 2D list -- Python

Question

I have a 2D list of characters in this fashion:

a = [['1','2','3'],
 ['4','5','6'],
 ['7','8','9']]

What's the most pythonic way to print the list as a whole block? I.e. no commas or brackets:

123
456
789

Answer 1

There are a lot of ways. Probably a str.join of a mapping of str.joins:

>>> a = [['1','2','3'],
... ['4','5','6'],
... ['7','8','9']]
>>> print('\n'.join(map(''.join, a)))
123
456
789
>>>

• Graviton: Oh right! Arrays, lists and arraylists... always screwing me up!
• Jean-François Fabre: Always here to try to improve an already good answer :) could be worth a bench to compare join(map('' vs join([''.join(x) for x in a]). In the latter, the outer join knows the size of the list and the items and allocates the output string in one go.
• juanpa.arrivillaga: @Jean-FrançoisFabre yeah, if performance really were an issue, probably materializing into a list will be faster. Likely, this code won't be performance critical. From the point of view of style and ease, I would be OK with this.
• Jean-François Fabre: compiled map makes up for the speed loss of the listcomp. A generator comprehension would be the slowest.
• juanpa.arrivillaga: If memory isn't a concern, the either the above or maybe print('\n'.join(list(map(''.join, a)))) if you are on Python 3. In any event, you can just benchmark with a couple large lists using the timeit module. Indeed, the "Basic examples" in the docs are very similar to your situation...

Answer 2

Best way in my opinion would be to use print function. With print function you won't require any type of joining and conversion(if all the objects are not strings).

>>> a = [['1','2','3'],
... ['4', 5, 6], # Contains integers as well.
... ['7','8','9']]
...
>>> for x in a:
... print(*x, sep='')
...
...
123
456
789

If you're on Python 2 then print function can be imported using from __future__ import print_function.

Answer 3

I'm a beginner learner, so please take my post with a few spoons of salt. But I have a better idea ( which includes printing a list with string+ integers)

D2List=[[1,2,3],[4,"Bingo",5],[6,7,8]]
for x,y,z in D2List:
 print ("x,y,z")

I got it working: https://github.com/Bahaa2468/Python/blob/22e6cfc9b478f9336ef0be283e2693c40f13d538/Bingo%20Game.Generator.py

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Answer 4

Like this:

import os
array = [['1','2','3'],
 ['4','5','6'],
 ['7','8','9']]
print(os.linesep.join(map(''.join, array)))

Answer 5

If you're looking for Pythonic then you surely need a generator comprehension:

print('\n'.join(''.join(i) for i in array))

• Jean-François Fabre: in the case of join, passing a list comprehension instead is faster because join creates one anyway (needs that to pre-compute the size): '\n'.join([''.join(i) for i in array]) even if it's uglier :)
• Chris: @Jean-FrançoisFabre Yup, here's where the conversion happens.
• Turn: Thanks for that @Jean-FrançoisFabre, I didn't know that. OTOH, the OP didn't ask for the fastest method. ;-)