Pretty print 2D list?

Question

Is there a simple, built-in way to print a 2D Python list as a 2D matrix?

So this:

[["A", "B"], ["C", "D"]]

would become something like

A    B
C    D

I found the pprint module, but it doesn't seem to do what I want.

I would have called that a 3D list. If you are willing to pull it in, `numpy` is pretty good about this sort of thing. — tacaswell, Nov 04 '12 at 00:20
See my answer at https://stackoverflow.com/a/65878050/13600624. — Ender, Jan 25 '21 at 02:05

georg · Accepted Answer · 2014-11-18T18:04:37.000

To make things interesting, let's try with a bigger matrix:

matrix = [
   ["Ah!",  "We do have some Camembert", "sir"],
   ["It's a bit", "runny", "sir"],
   ["Well,",  "as a matter of fact it's", "very runny, sir"],
   ["I think it's runnier",  "than you",  "like it, sir"]
]

s = [[str(e) for e in row] for row in matrix]
lens = [max(map(len, col)) for col in zip(*s)]
fmt = '\t'.join('{{:{}}}'.format(x) for x in lens)
table = [fmt.format(*row) for row in s]
print '\n'.join(table)

Output:

Ah!                     We do have some Camembert   sir            
It's a bit              runny                       sir            
Well,                   as a matter of fact it's    very runny, sir
I think it's runnier    than you                    like it, sir

UPD: for multiline cells, something like this should work:

text = [
    ["Ah!",  "We do have\nsome Camembert", "sir"],
    ["It's a bit", "runny", "sir"],
    ["Well,",  "as a matter\nof fact it's", "very runny,\nsir"],
    ["I think it's\nrunnier",  "than you",  "like it,\nsir"]
]

from itertools import chain, izip_longest

matrix = chain.from_iterable(
    izip_longest(
        *(x.splitlines() for x in y), 
        fillvalue='') 
    for y in text)

And then apply the above code.

See also http://pypi.python.org/pypi/texttable

genius! BUT what if we want multiple lines within each cell i.e. a 3D array :) — CpILL, Nov 16 '14 at 01:06
@CpILL: one option would be to unzip 3D into a 2D: `[[[a,b,c],[xyz]]]=>[[a,x],[b,y],[c,z]]` and then apply the above. — georg, Nov 16 '14 at 08:50

score 53 · Answer 2 · edited Mar 31 '16 at 18:04

53

If you can use Pandas (Python Data Analysis Library) you can pretty-print a 2D matrix by converting it to a DataFrame object:

from pandas import *
x = [["A", "B"], ["C", "D"]]
print DataFrame(x)

   0  1
0  A  B
1  C  D

edited Mar 31 '16 at 18:04

Alceu Costa

9,525
19
63
78

answered Aug 22 '15 at 18:36

sten

6,266
8
35
48

9

While this answer is probably correct and useful, it is preferred if you [include some explanation along with it](http://meta.stackexchange.com/q/114762/159034) to explain how it helps to solve the problem. This becomes especially useful in the future, if there is a change (possibly unrelated) that causes it to stop working and users need to understand how it once worked. – Kevin Brown-Silva Aug 22 '15 at 18:48
3

This is exactly what I wanted. Thanks. – Arvind Jan 22 '18 at 07:31

Rodrigo López · Answer 3 · 2020-03-10T11:18:52.677

47

For Python 3 without any third part libs:

matrix = [["A", "B"], ["C", "D"]]

print('\n'.join(['\t'.join([str(cell) for cell in row]) for row in matrix]))

Output

A   B
C   D

edited Mar 10 '20 at 11:18

answered May 09 '18 at 16:06

Rodrigo López

3,689
1
18
25

underrated answer right here. Works great, keeps it native, one line FTW. – alphazwest Nov 07 '21 at 16:22
My only regret is that I have but one upvote to give for this answer – DanWebster Dec 10 '21 at 15:36
We should give a medal to this guy. – Philippe Remy Feb 01 '22 at 12:22

score 37 · Answer 4 · edited Jul 05 '19 at 00:33

37

You can always use numpy:

import numpy as np
A = [['A', 'B'], ['C', 'D']]
print(np.matrix(A))

Output:

[['A' 'B']
 ['C' 'D']]

edited Jul 05 '19 at 00:33

Sash Sinha

15,168
3
22
38

answered Apr 11 '16 at 01:48

Souradeep Nanda

2,763
1
32
39

2

showing the output for comparison with other solutions would be a 'nice to have' – vwvan Mar 16 '19 at 01:29
1

Use `print(np.array(A))` to avoid warnings – lingjiankong Jun 29 '20 at 03:54

score 9 · Answer 5 · edited Jun 20 '20 at 09:12

Just to provide a simpler alternative to print('\n'.join(\['\t'.join(\[str(cell) for cell in row\]) for row in matrix\])) :

matrix = [["A", "B"], ["C", "D"]]
for row in matrix:
    print(*row)

Explanation *row unpacks row, so print("A", "B") is called when row is ["A", "B"], for example.

Note Both answers will only be formatted nicely if each column has the same width. To change the delimiter, use the sep keyword. For example,

for row in matrix:
    print(*row, sep=', ')

will print

A, B
C, D

instead.

One-liner without a for loop

print(*(' '.join(row) for row in matrix), sep='\n')

' '.join(row) for row in matrix) returns a string for every row, e.g. A B when row is ["A", "B"].

*(' '.join(row) for row in matrix), sep='\n') unpacks the generator returning the sequence 'A B', 'C D', so that print('A B', 'C D', sep='\n') is called for the example matrix given.

score 6 · Answer 6 · answered Aug 22 '15 at 20:47

A more lightweight approach than pandas is to use the prettytable module

from prettytable import PrettyTable

x = [["A", "B"], ["C", "D"]]

p = PrettyTable()
for row in x:
    p.add_row(row)

print p.get_string(header=False, border=False)

yields:

A B
C D

prettytable has lots of options to format your output in different ways.

See https://code.google.com/p/prettytable/ for more info

score 3 · Answer 7 · answered Sep 10 '20 at 17:02

If you're using a Notebook/IPython environment, then sympy can print pleasing matrices using IPython.display:

import numpy as np
from sympy import Matrix, init_printing
init_printing()

print(np.random.random((3,3)))
display(np.random.random((3,3)))
display(Matrix(np.random.random((3,3))))

score 1 · Answer 8 · answered Dec 10 '20 at 22:04

I would also recommend tabulate, which can optionally print headers too:

from tabulate import tabulate

lst = [['London', 20],['Paris', 30]]
print(tabulate(lst, headers=['City', 'Temperature']))

:

City      Temperature
------  -------------
London             20
Paris              30

Omar · Answer 9 · 2022-05-01T21:20:28.047

1

Without any third party libraries, you could do:

matrix = [["A", "B"], ["C", "D"]]
print(*matrix, sep="\n")

Output:

['A', 'B']
['C', 'D']

edited May 01 '22 at 21:20

answered Apr 27 '22 at 13:03

Omar

101
3

score 0 · Answer 10 · edited Apr 02 '21 at 14:05

0

You can update print's end=' ' so that it prints space instead of '\n' in the inner loop and outer loop can have print().

a=[["a","b"],["c","d"]]
for i in a:
  for j in i:
    print(j, end=' ')
  print()

I found this solution from here.

edited Apr 02 '21 at 14:05

Ynjxsjmh

16,448
3
17
42

answered Dec 23 '18 at 06:57

Sandeep

106
1
4

score -2 · Answer 11 · edited Jan 15 '18 at 12:30

-2

See the following code.

# Define an empty list (intended to be used as a matrix)
matrix = [] 
matrix.append([1, 2, 3, 4])
matrix.append([4, 6, 7, 8])
print matrix
# Now just print out the two rows separately
print matrix[0]
print matrix[1]

edited Jan 15 '18 at 12:30

Community

1
1

answered Jan 13 '18 at 14:30

jfconroy

17
2

try this and see what happens does not sound like an answer. Please review: https://stackoverflow.com/help/how-to-answer – Daniel Jan 13 '18 at 14:48

Pretty print 2D list?

11 Answers11

Linked

Related