perl to python

[Duncan Booth]

Scott Schwartz <"schwartz+ at usenet "@bio.cse.psu.edu> wrote in
news:8gisf1ihvc.fsf at galapagos.bx.psu.edu: 

> Duncan Booth <me at privacy.net> writes:
>> import sys
>> for line in sys.stdin:
>>     line = line[:-1].split('\t')
>>     print "%s %s %s %s" % (line[3], line[2], line[1], line[0])
> 
>> While I agree with you that using the appropriate tool is preferred
>> over using Python for everything, I don't really see much to choose
>> between the Python and awk versions here.
> 
> 1) Python throws an error if you have less than three fields,
> requiring more typing to get the same effect.

I would rather have the error when the input isn't formatted as expected. 
The alternative would be incorrect output.

If you really want to suppress the error then:

     line = (line[:-1]+'\t'*3).split('\t')

> 
> 2) Python generators on stdin behave strangely.  For one thing,
> they're not properly line buffered, so you don't get any lines until
> eof.  But then, eof is handled wrongly, and the loop doesn't exit.

True, if you are trying to reformat interactive input. I had assumed that 
the use case here was redirecting input from a file, and in that case the 
EOF problem isn't an issue. Buffering may or may not be a problem.

> 
> 3) There is no efficient RS equivalent, in case you need to read
> paragraphs.

In that case I would write a generator to group the lines. Longer than RS, 
but also more flexible.