Pretty print 2D list?
PythonMatrixPython Problem Overview
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.
Python Solutions
Solution 1 - Python
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.
Solution 2 - Python
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
Solution 3 - Python
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
Solution 4 - Python
You can always use numpy:
import numpy as np
A = [['A', 'B'], ['C', 'D']]
print(np.matrix(A))
Output:
[['A' 'B']
['C' 'D']]
Solution 5 - Python
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.
Solution 6 - Python
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
Solution 7 - Python
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))))
Solution 8 - Python
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
Solution 9 - Python
Without any third party libraries, you could do:
matrix = [["A", "B"], ["C", "D"]]
print(*matrix, sep="\n")
Output:
['A', 'B']
['C', 'D']
Solution 10 - Python
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.
Solution 11 - Python
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]