Re: Any algorithm to preserve whitespaces?
 

Santosh Kumar wrote:

> Yes, Peter got it right.
>
> Now, how can I replace:
>
> script, givenfile = argv
>
> with something better that takes argv[1] as input file as well as
> reads input from stdin.
>
> By input from stdin, I mean that currently when I do `cat foo.txt |
> capitalizr` it throws a ValueError error:
>
> Traceback (most recent call last):
> File "/home/santosh/bin/capitalizr", line 16, in <module>
> script, givenfile = argv
> ValueError: need more than 1 value to unpack
>
> I want both input methods.

You can use argparse and its FileType:

import argparse
import sys

parser = argparse.ArgumentParser()
parser.add_argument("infile", type=argparse.FileType("r"), nargs="?",
default=sys.stdin)
args = parser.parse_args()

for line in args.infile:
print line.strip().title() # replace with your code


As this has the small disadvantage that infile is opened immediately I tend
to use a slight variation:

import argparse
import sys
from contextlib import contextmanager

@contextmanager
def xopen(filename):
if filename is None or filename == "-":
yield sys.stdin
else:
with open(filename) as instream:
yield instream

parser = argparse.ArgumentParser()
parser.add_argument("infile", nargs="?")
args = parser.parse_args()

with xopen(args.infile) as instream:
for line in instream:
print line.strip().title()