Align columns in a text file

Question

I have a plain text file that contains user login data:

dtrapani  HCPD-EPD-3687  Mon  05/13/2013    9:47:01.72
dlibby  HCPD-COS-4611  Mon  05/13/2013    9:49:34.55
lmurdoch  HCPD-SDDEB-3736  Mon  05/13/2013    9:50:38.48
lpatrick  HCPD-WIN7-015  Mon  05/13/2013    9:57:44.57
mlay  HCPD-WAR-3744  Mon  05/13/2013  10:00:07.94
eyoung  HCPD-NLCC-0645  Mon  05/13/2013  10:03:01.83

I'm trying to print the data in left- and right-aligned columns:

dtrapani  HCPD-EPD-3687    Mon  05/13/2013    9:47:01.72
dlibby    HCPD-COS-4611    Mon  05/13/2013    9:49:34.55
lmurdoch  HCPD-SDDEB-3736  Mon  05/13/2013    9:50:38.48
lpatrick  HCPD-WIN7-015    Mon  05/13/2013    9:57:44.57
mlay      HCPD-WAR-3744    Mon  05/13/2013   10:00:07.94
eyoung    HCPD-NLCC-0645   Mon  05/13/2013   10:03:01.83

How can I do this?

This is the code I have so far:

with open(r'C:\path\to\logons.txt', 'r') as f:
    for line in f:
        data = line.strip()
        print(data)

Answer 1

I would go for the new(er) print formatter with this one (assuming your fields are consistent). The print/format statement is pretty easy to use and can be found here. Since your data can be seen as a list, you can do a single call to format and supplying the correct formatter data you'll get your output. This has a bit more fine grained control than ljust or rjust but has the downside that you need to know that your data coming in is consistent.

with open(r'C:\path\to\logons.txt', 'r') as f:
    for line in f:
        data = line.split()    # Splits on whitespace
        print '{0[0]:<15}{0[1]:<15}{0[2]:<5}{0[3]:<15}{0[4]:>15}'.format(data)

Answer 2

str.ljust(width, [fillchar=" "]) (http://docs.python.org/2/library/stdtypes.html#str.ljust) seems like what you're after. Left justify each field when printing to the maximum length + a little bit.

For the last field to match your example, you'll want to right justify it instead using rjust.

Answer 3

#!/usr/bin/env python
import sys
inputfile = '''dtrapani HCPD-EPD-3687 Mon 05/13/2013 9:47:01.72
dlibby HCPD-COS-4611 Mon 05/13/2013 9:49:34.55
lmurdoch HCPD-SDDEB-3736 Mon 05/13/2013 9:50:38.48
lpatrick HCPD-WIN7-015 Mon 05/13/2013 9:57:44.57
mlay HCPD-WAR-3744 Mon 05/13/2013 10:00:07.94
eyoung HCPD-NLCC-0645 Mon 05/13/2013 10:03:01.83'''.split('\n')
output = sys.stdout
lengths = [10,17,5,14,0]
for line in inputfile:
    line = line.split()
    for field, fieldlength in zip(line,lengths):
        output.write(field.ljust(fieldlength))
    output.write('\n')

Answer 4

As of Python 3.6+

Use the modern f-string syntax:

with open(r'logons.txt', 'r') as f:
    for line in f:
        s = line.split()
        print(f'{s[0]:<10}{s[1]:<17}{s[2]:<5}{s[3]:<12}{s[4]:>12}')
        #     ^       ^^^       ^^^       ^^       ^^^       ^^^
        # f-string  left-10   left-17   left-5   left-12   right-12

• much faster than the older str.format
• follows the same format specifications

---

Output:

dtrapani  HCPD-EPD-3687    Mon  05/13/2013    9:47:01.72
dlibby    HCPD-COS-4611    Mon  05/13/2013    9:49:34.55
lmurdoch  HCPD-SDDEB-3736  Mon  05/13/2013    9:50:38.48
lpatrick  HCPD-WIN7-015    Mon  05/13/2013    9:57:44.57
mlay      HCPD-WAR-3744    Mon  05/13/2013   10:00:07.94
eyoung    HCPD-NLCC-0645   Mon  05/13/2013   10:03:01.83