A simple python class to (adaptively) align text lines based on tab characters ('\t') in real time.

output.txt

Column 1 Header Col2 Col3
Shorter 1       Col2 Col3
Longer message on column 1 Col2 Col3
Again shorter 1            Col2 Col3
Longer message on column 1 Col2 Col3
Something in between       Col2 Col3
Something in between v2    I didn't move ! But now I did
Something in between v10   shorter         Now I didn't move either
Everything in between      from now on     will be aligned
Until you call             t.reset()
like this, see ?
test 1     test 2
test 10    test 20
Use it with unknown length variables like this:
Sending request to: example.com and waiting for reply on 123
Sending request to: linux.org   and waiting for reply on 123
Sending request to: superlongurl.long.tld.too and waiting for reply on 123
Sending request to: wikipedia.com             and waiting for reply on 123
Sending request to: notsolongurl.tld          and waiting for reply on 123
Sending request to: github.com                and waiting for reply on 123
Sending request to: git-scm.com               and waiting for reply on 123
You can also        avoid modifying the existing layout by calling t.over() instead of t().

SmartTabs.py

class SmartTabs:

    def __init__(self):
        self.columns = [0]

    def __call__(self, line):
        cells = line.split('\t')
        cols  = self.columns

        # Pad as needed or update existing columns
        for a in range(0, min(len(cells), len(cols))):
            padding = cols[a] - len(cells[a])
            if padding > 0:
                cells[a] += ' ' * padding
            else:
                cols[a]  += -padding

        # Add new columns if needed
        for b in range(a + 1, len(cells)):
            cols.append(len(cells[b]))

        return ''.join(cells)

    def over(self, line):
        cells = line.split('\t')
        cols  = self.columns

        # Pad as needed, but don't update existing columns
        for a in range(0, min(len(cells), len(cols))):
            padding = cols[a] - len(cells[a])
            if padding > 0:
                cells[a] += ' ' * padding

        return ''.join(cells)

    def reset(self):
        self.columns = [0]

t = SmartTabs()

test.py

# Usage:
from SmartTabs import t
print(t('Column 1 Header\t Col2\t Col3'))
print(t('Shorter 1\t Col2\t Col3'))
print(t('Longer message on column 1\t Col2\t Col3'))
print(t('Again shorter 1\t Col2\t Col3'))
print(t('Longer message on column 1\t Col2\t Col3'))
print(t('Something in between\t Col2\t Col3'))
print(t('Something in between v2\t I didn\'t move !\t But now I did'))
print(t('Something in between v10\t shorter\t Now I didn\'t move either'))
print(t('Everything in between\t from now on\t will be aligned'))
print(t('Until you call\t t.reset()'))
t.reset()
print(t('like this,\t see ?'))
print(t('test 1\t test 2'))
print(t('test 10\t test 20'))
print('Use it with unknown length variables like this:')
for url in ['example.com', 'linux.org', 'superlongurl.long.tld.too', 'wikipedia.com', 'notsolongurl.tld', 'github.com', 'git-scm.com']:
    print(t('Sending request to:\t {0}\t and waiting for reply on {1}'.format(url, 123)))
print(t.over('You can also\t avoid modifying the existing layout by calling t.over() instead of t().'))