Pipe output from shell command to a python script

If you want your script to behave like many unix command line tools and accept a pipe or a filename as first argument, you can use the following:

#!/usr/bin/env python
import sys

# use stdin if it's full                                                        
if not sys.stdin.isatty():
    input_stream = sys.stdin

# otherwise, read the given filename                                            
else:
    try:
        input_filename = sys.argv[1]
    except IndexError:
        message = 'need filename as first argument if stdin is not full'
        raise IndexError(message)
    else:
        input_stream = open(input_filename, 'rU')

for line in input_stream:
    print(line) # do something useful with each line

You need to read from stdin to retrieve the data in the python script e.g.

#!/usr/bin/env python

import sys

def hello(variable):
    print variable

data = sys.stdin.read()
hello(data)

If all you want to do here is grab some data from a mysql database and then manipulate it with Python I would skip piping it into the script and just use the Python MySql module to do the SQL query.