编写空格分隔的文本以使其在Python＃2中易于阅读

Question

I want to write a 2D numpy array into a human-readable text file format. I came across this question asked before but it only specifies equal number of space to be associated with each element in the array. In it all elements are spaced out with 10 spaces. What I want is different number of space for each column in my array.

Writing white-space delimited text to be human readable in Python

For example, I want 7 spaces for my 1st column, 10 spaces for my 2nd column, 4 spaces for my 3rd column, etc. Is there an analogy to numpy.savetxt(filename, X, delimiter = ',', fmt = '%-10s'), but where instead of '%-10s' I have say '%-7s, %-10s, %-4s' etc?

Thank you

Answer 1

Here is an example of what it can look like (Python2&3):

l = [[1,2,3,4], [3,4,5,6]]
for row in l:
    print(u'{:<7} {:>7} {:^7} {:*^7}'.format(*row))

1             2    3    ***4***
3             4    5    ***6***

The formatting options are taken from http://docs.python.org/2/library/string.html

>>> '{:<30}'.format('left aligned')
'left aligned                  '
>>> '{:>30}'.format('right aligned')
'                 right aligned'
>>> '{:^30}'.format('centered')
'           centered           '
>>> '{:*^30}'.format('centered')  # use '*' as a fill char
'***********centered***********'

If you need a file, then do this:

l = [[1,2,3,4], [3,4,5,6]]
with open('file.txt', 'wb') as f:
    f.write(u'\ufeff'.encode('utf-8'))
    for row in l:
        line = u'{:<7} {:>7} {:^7} {:*^7}\r\n'.format(*row)
        f.write(line.encode('utf-8'))

The content of the file is

1             2    3    ***4***
3             4    5    ***6***

And the encoding is UTF-8. This means that you can have not only numbers but also any letter in your heading: ☠ ⇗ ⌚ ② ☕ ☃ ⛷

heading = [u'☠', u'⇗', u'⌚', u'②']
with open('file.txt', 'wb') as f:
    f.write(u'\ufeff'.encode('utf-8'))
    line = '{:<7} {:>7} {:^7} {:*^7}\r\n'.format(*heading)
    f.write(line.encode('utf-8'))
    for row in l:
        line = '{:<7} {:>7} {:^7} {:*^7}\r\n'.format(*row)
        f.write(line.encode('utf-8'))

☠             ⇗    ⌚    ***②***
1             2    3    ***4***
2             3    4    ***5***