CODEWITHSUNDEEP
pythonmatrix
houbysoft
houbysoft

Reputation: 33392

Pretty print 2D list?

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.

Upvotes: 101

Views: 173314

Answers (12)

sten
sten

Reputation: 7476

You can use pandas to pretty-print a 2D matrix by converting it to a DataFrame object:

import pandas as pd
x = [["A", "B"], ["C", "D"]]
print(pd.DataFrame(x))


   0  1
0  A  B
1  C  D

Upvotes: 58

ᴇɴᴅᴇʀᴍᴀɴ
ᴇɴᴅᴇʀᴍᴀɴ

Reputation: 384

A simpler way is to do it using the "end" parameter in print(). This works only because in Python (and in many other languages), all letters are the same width.

table = [["A", "BC"], ["DEFG", "HIJ"]]
for row in table:
    for col in row:
        spaces = 5 #adjust as needed
        spaces -= (len(col) - 1) #spaces everything out
        print(col, end = " " * spaces)
    print() #add line break before next row

The "end" function sets what will be printed after the end of the arguments, as the default is \n.

As you can see, I offseted how many spaces there are according to the length of each item in each row.

Upvotes: 1

Maokai
Maokai

Reputation: 214

Without any third party libraries, you could do:

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

Output:

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

Upvotes: 15

Sandeep
Sandeep

Reputation: 106

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.

Upvotes: 0

Reveille
Reveille

Reputation: 4619

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

Upvotes: 4

ZSG
ZSG

Reputation: 1379

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))))

enter image description here

Upvotes: 7

Rodrigo López
Rodrigo López

Reputation: 4259

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

Upvotes: 75

LHeng
LHeng

Reputation: 601

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.

Upvotes: 13

Souradeep Nanda
Souradeep Nanda

Reputation: 3288

You can always use numpy:

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

Output:

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

Upvotes: 42

jfconroy
jfconroy

Reputation: 13

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]

Upvotes: -4

Dov Grobgeld
Dov Grobgeld

Reputation: 4983

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

Upvotes: 6

georg
georg

Reputation: 214949

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

Upvotes: 102

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