[Tutor] creating a regularly placed fields in a line

[Prasad, Ramit]

> I wrote a small piece of code (given below). The aim is to take each line
> in a file, split the fields, replace the first four fields and then write
> the new lines in a output file. The input and output are given in the
> attached file. The output contains fields which are irregularly placed
> depending up on the size of the field. I am thinking to fix the size of
> each field. Kindly provide me some way on how i can do the same or a
> better way to fix placement of fields.
> 
> with open('tmp') as tp:
>     for line in tp:
>         line=line.split()
>         p1=atm_type[line[0]];p2=atm_type[line[1]]
>         p3=atm_type[line[2]];p4=atm_type[line[3]]
>         new='\t'.join(line[4:10])
>         bond.write('   %s\t%s\t%s\t%s\t%s\n' % (p1,p2,p3,p4,new) )

Taking a look at your output file leads me think that it is 
not really meant to be human readable. If it is only for a 
program to use, then I would just make it comma separated
using the csv module. If you are intending to make it readable
to humans, I would suggest looking at string formatting. 
It is better than tabbing since most clients show tabs a 
little differently and a tab may still cause irregular
columns if you have a large difference in each row's
column size. The formatting mini-language can be a little 
complex but luckily the guide is useful.
http://docs.python.org/library/string.html#format-specification-mini-language 

The examples on that page are useful and I think what you 
want is quoted below.
"
Aligning the text and specifying a width:
>>> '{:<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***********'
"

Not really sure how to do the equivalent with % substitution.

Ramit


Ramit Prasad | JPMorgan Chase Investment Bank | Currencies Technology
712 Main Street | Houston, TX 77002
work phone: 713 - 216 - 5423

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