user2829468 user2829468 - 1 month ago 8
Python Question

How to make matrices in Python?

I've googled it and searched StackOverflow and YouTube.. I just can't get matrices in Python to click in my head. Can someone please help me? I'm just trying to create a basic 5x5 box that displays:

A A A A A
B B B B B
C C C C C
D D D D D
E E E E E


I got

a b c d e
a b c d e
a b c d e
a b c d e
a b c d e


To display but I couldn't even get them to break lines that, instead all they would appear as

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


And if I try to add \n to them or print "" etc it just doesn't work.. \n will display as 'A\n' and print will display before the matrix.

Please someone help me, even if you direct me to somewhere that should be really obvious and make me look like an idiot, I just want to learn this.

Answer

Looping helps:

for row in matrix:
    print ' '.join(row)

or use nested str.join() calls:

print '\n'.join([' '.join(row) for row in matrix])

Demo:

>>> matrix = [['A', 'B', 'C', 'D', 'E'], ['A', 'B', 'C', 'D', 'E'], ['A', 'B', 'C', 'D', 'E'], ['A', 'B', 'C', 'D', 'E'], ['A', 'B', 'C', 'D', 'E']]
>>> for row in matrix:
...     print ' '.join(row)
... 
A B C D E
A B C D E
A B C D E
A B C D E
A B C D E
>>> print '\n'.join([' '.join(row) for row in matrix])
A B C D E
A B C D E
A B C D E
A B C D E
A B C D E

If you wanted to show the rows and columns transposed, transpose the matrix by using the zip() function; if you pass each row as a separate argument to the function, zip() recombines these value by value as tuples of columns instead. The *args syntax lets you apply a whole sequence of rows as separate arguments:

>>> for cols in zip(*matrix):  # transposed
...     print ' '.join(cols)
... 
A A A A A
B B B B B
C C C C C
D D D D D
E E E E E