Align numbers in sublist

Question

I have a set of numbers that I want to align considering the comma:

   10    3          
  200    4000,222  3  1,5 
  200,21          0,3  2   
30000    4,5      1      

mylist = [['10', '3', '', ''], 
          ['200', '4000,222', '3', '1,5'], 
          ['200,21', '', '0,3', '2'], 
          ['30000', '4,5', '1', '']]

What I want is to align this list considering the comma:

expected result:

mylist = [['   10   ', '   3    ', '   ', '   '], 
          ['  200   ', '4000,222', '3  ', '1,5'], 
          ['  200,21', '        ', '0,3', '2  '], 
          ['30000   ', '   4,5  ', '1  ', '   ']]

I tried to turn the list:

mynewlist = list(zip(*mylist))  

and to find the longest part after the comma in every sublist:

for m in mynewlist:
    max([x[::-1].find(',') for x in m]

and to use rjust and ljust but I don't know how to ljust after a comma and rjust before the comma, both in the same string.

How can I resolve this without using format()? (I want to align with ljust and rjust)

Answer 1

Here's another approach that currently does the trick. Unfortunately, I can't see any simple way to make this work, maybe due to the time :-)

Either way, I'll explain it. r is the result list created before hand.

r = [[] for i in range(4)]

Then we loop through the values and also grab an index with enumerate:

for ind1, vals in enumerate(zip(*mylist)):

Inside the loop we grab the max length of the decimal digits present and the max length of the word (the word w/o the decimal digits):

    l = max(len(v.partition(',')[2]) for v in vals) + 1
    mw = max(len(v if ',' not in v else v.split(',')[0]) for v in vals)

Now we go through the values inside the tuple vals and build our results (yup, can't currently think of a way to avoid this nesting).

    for ind2, v in enumerate(vals):

If it contains a comma, it should be formatted differently. Specifically, we rjust it based on the max length of a word mw and then add the decimal digits and any white-space needed:

        if ',' in v:
            n, d = v.split(',')
            v = "".join((n.rjust(mw),',', d, " " * (l - 1 - len(d))))

In the opposite case, we simply .rjust and then add whitespace:

        else:
            v = "".join((v.rjust(mw) + " " * l))

finally, we append to r.

        r[ind1].append(v)

All together:

r = [[] for i in range(4)]
for ind1, vals in enumerate(zip(*mylist)):
    l = max(len(v.partition(',')[2]) for v in vals) + 1
    mw = max(len(v if ',' not in v else v.split(',')[0]) for v in vals)
    for ind2, v in enumerate(vals):
        if ',' in v:
            n, d = v.split(',')
            v = "".join((n.rjust(mw),',', d, " " * (l - 1 - len(d))))
        else:
            v = "".join((v.rjust(mw) + " " * l))
        r[ind1].append(v)

Now, we can print it out:

>>> print(*map(list,zip(*r)), sep='\n)
['   10   ', '   3    ', '   ', '   ']
['  200   ', '4000,222', '3  ', '1,5']
['  200,21', '        ', '0,3', '2  ']
['30000   ', '   4,5  ', '1  ', '   ']