How can I produce a nice output of a numpy matrix?

Question

I currently have the following snippet:

#!/usr/bin/python
# -*- coding: utf-8 -*-

import numpy
from numpy import linalg

A = [[1,2,47,11],[3,2,8,15],[0,0,3,1],[0,0,8,1]]
S = [[113,49,2,283],[-113,0,3,359],[0,5,0,6],[0,20,0,12]]

A = numpy.matrix(A)
S = numpy.matrix(S)

numpy.set_printoptions(precision=2, suppress=True, linewidth=120)
print("S^{-1} * A * S")
print(linalg.inv(S) * A * S)

which produces this output:

Is there a standard way to produce an output similar to the following? How can I get this output?

[[ -1    -0.33  0  0]
 [  0     1     0  0]
 [  0  -648     4  0]
 [  0     6.67  0  5]]

What's different?

• At least two spaces between the last character of column i and the first character of column i+1, but it might be more if more is needed (NumPy output makes two spaces)
• the dots are aligned (The are aligned, but the font setting of BetterPythonConsole messes it up)
• No -0 but 0
• No 0. but 0

edit: It seems as if the Python Console, which gets started with gEdits BetterPythonConsole plugin does something different than Python, when I start it from terminal.

This is the output as text of the script above

moose@pc07:~/Desktop$ python matrixScript.py 
S^{-1} * A * S
[[  -1.     -0.33    0.     -0.  ]
 [   0.     -1.     -0.      0.  ]
 [   0.   -648.      4.     -0.  ]
 [   0.      6.67    0.      5.  ]]

With prettyprint:

S^{-1} * A * S
matrix([[  -1.  ,   -0.33,    0.  ,   -0.  ],
        [   0.  ,   -1.  ,   -0.  ,    0.  ],
        [   0.  , -648.  ,    4.  ,   -0.  ],
        [   0.  ,    6.67,    0.  ,    5.  ]])

This is defenitely worse, but it was worth a try.

Solution

If you use numpy 1.8.x you can customize formatting with the formatter parameter. For example, setting:

numpy.set_printoptions(formatter={'float': lambda x: 'float: ' + str(x)})

All floats would be printed like float: 3.0, or float: 12.6666666666.

Unfortunately I still have numpy 1.6.1 installed and this option is not provided, so I'm not able to use it to get your desired output.

Comments

[Martin Thoma]

I guess updating my system would be the best option as all other problems in the formating seem to be related to BetterPythonConsole.

[Bakuriu]

Yes, probably the other option would be to write a custom format function to be used with numpy arrays. Which may not be too hard to write, but if you want to make it a bit general for possible future uses it's not something you write in 2 minutes. Hopefully the upgrade will give you other benefits other than this one.