How to insert tab into the output to a file in Python?

Question

How do I insert a tab into the output to a file in Python?

For example,

  print >>outPutFile , c.lstrip()+"\t"+d.rstrip('\n')+"\t"+a+"\t"+b

Output:

  cfn79e739_1.lp  260175  79      739

  cfn100e1217_1.lp        288734  100     1217

The second line has no tab after 288734. Why?

The first line has no tab after cfn79e739_1.lp and 260175. Why?

I need to make each column at the same alignment.

There is a tab in your output (everything is aligned to 8th columns). — Howard
– Howard, Commented Jan 8, 2012 at 18:30
Unrelated notes: (1) The Python way of adding all these tabs would be '\t'.join([c.lstrip(), d.rstrip(…),…]). (2) Your d.rstrip('\n') could probably be simplified (and made a bit more powerful) as d.rstrip(), which also strips whitespace. — Eric O. Lebigot
– Eric O. Lebigot, Commented Jan 8, 2012 at 19:50

ekhumoro · Accepted Answer · 2012-01-08 19:37:14Z

3

Work out the maximum width for each column, and then pad each value accordingly:

lines = [
    ['cfn79e739_1.lp', '260175', '79', '739'],
    ['cfn100e1217_1.lp', '285768', '100', '1217'],
    ['cfn200e11660_1.lp', '288734', '200', '11660'],
    ['cfn1500e145_1.lp', '218435', '1500', '145'],
    ]

def print_columns(lines, spacing=2):
    widths = [max(len(value) for value in column) + spacing
              for column in zip(*lines)]
    for line in lines:
        print(''.join('%-*s' % item for item in zip(widths, line)))

print_columns(lines)

Output:

cfn79e739_1.lp     260175  79    739    
cfn100e1217_1.lp   285768  100   1217   
cfn200e11660_1.lp  288734  200   11660  
cfn1500e145_1.lp   218435  1500  145

answered Jan 8, 2012 at 19:37

ekhumoro

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1 Comment

Eric O. Lebigot Over a year ago

+1: very good solution. Indeed, tabulations are not a solution to the original question.

Ignacio Vazquez-Abrams · Accepted Answer · 2012-01-08 18:32:36Z

2

Yes it does. But that's not how tabs work. They move the cursor to the next column that is a multiple of eight. If you want perfectly tabular alignment then you should use string interpolation or formatting with a known size.

>>> print '%-20s %-4d' % ('foo', 42)
foo                  42  
>>> print '%-20s %-4d' % ('bar', 13)
bar                  13

answered Jan 8, 2012 at 18:32

Ignacio Vazquez-Abrams

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1 Comment

Eric O. Lebigot Over a year ago

No downvote, but tabs do not always "move the cursor to the next column by a multiple of 8" (you can for instance ask the less pager to put tabs at any multiple); this sentence should be qualified, at the very least.

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