I have the following code:
import numpy as np
from numpy import matrix
MM = matrix([[1.00,0,0],[0,1.50,0],[0,0,2.00]])
M = np.array(MM)
print("matrix M: \n", M)
which output looks like this:
matrix M:
[[1. 0. 0. ]
[0. 1.5 0. ]
[0. 0. 2. ]]
This is very aesthetic, but I want it to look more organized. Something like this hopefully:
[1. 0. 0.]
[0. 1.5 0.]
[0. 0. 2.]
If you print M on its own it actually looks as you expect.
The reason why the first line gets messed up is because print inserts a space between its arguments by default. You can suppress that by providing sep=''.
See https://docs.python.org/3/library/functions.html#print for reference.
Or better yet, omit \n from the first print argument and use sep='\n' instead:
>>> print("matrix M:", M, sep='\n')
matrix M:
[[1. 0. 0. ]
[0. 1.5 0. ]
[0. 0. 2. ]]
Pretty close:
'\n'.join('[{}]'.format(' '.join(str(n) for n in row)) for row in M)
Outputs
[1.0 0.0 0.0]
[0.0 1.5 0.0]
[0.0 0.0 2.0]
This removes the indentation and the double square brackets.
However, with very large matrices this might be slow due to the nested for loops.
As describes here Pretty print 2D Python list , a very nice option is the following:
s = [[str(e) for e in row] for row in M]
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))
1.0 0.0 0.0
0.0 1.5 0.0
0.0 0.0 2.0
The exact desired output is this:
print('\n'.join('[{}]'.format('. '.join(str(float(n)) for n in row)) for row in M))
[1.0. 0.0. 0.0]
[0.0. 1.5. 0.0]
[0.0. 0.0. 2.0]
Depending on how much extra code/complexity you want for a solution here, you can do a few things. You can use a custom function in the print statement if you really want fine-grained control over the output (using code offered up in some of the other proposed solutions), but a less cumbersome approach that still gives you a decent amount of flexibility is to use the array2string function already included in Numpy.
A few examples using your scenario:
>>> print(np.array2string(a=M))
[[1. 0. 0. ]
[0. 1.5 0. ]
[0. 0. 2. ]]
separator argument to add a bit of padding around elements:>>> print(np.array2string(a=M, separator=' '))
[[1. 0. 0. ]
[0. 1.5 0. ]
[0. 0. 2. ]]
print statement (array2string doesn't give you a way to change this) itself, doing a bit of manipulation to account for the character spacing with the brackets being removed:>>> print(' ' + np.array2string(a=M, separator=' ')[1:-1])
[1. 0. 0. ]
[0. 1.5 0. ]
[0. 0. 2. ]
Note that the last scenario still leaves a space at the beginning of each line. You could use regexes to clean this up.
I realize that this may not be exactly what you are looking for in terms of output, but I thought I might offer up a lighter weight alternative that gets you mostly there.
Min the output withprint("matrix M: \n", M, sep=''). But you'll still have the outer square brackets.np.matrixis always 2d, but other numpy arrays may be 1d or 3d.