Python Grep (was: writing (Gnu)MAKE in Python)

[Doug Stanfield]

[John said:]
> > ...I would like to have Bash, sed, and grep as Python
> > programs rather than compiled C.
> 
[and Corageous asked:]
> Why?

Consider this an attempt at translation.

There have been posts in the past about having a Python shell.  Perhaps
thats what John wants.  Not that I'd like that.  It may be that John wants
the functionality of sed and grep more easily accessible in Python.  That is
something I care about (thus the self serving attempt at manipulating this
thread. ;-)

Grep functions in particular are something that I wonder about.  The
following is an experiment:

#!/usr/bin/python
#
#       pygrep.py
#
#
"""     An attempt to compare the use of the grep
        command with a 'Pythonic' method of finding
        all lines in a file that contain a string.
"""
import string, os

def pygrep(the_string,the_file):
    """ Search for and return all occurrances of lines
        in the_file that contain the_string.
        This is simplistic and unprotected but its
        purpose is only to learn how to make it fast. """

    find = string.find

    holder = open(the_file,'r')
    while 1:
        line = holder.readline()
        if not line:
            break
        if find(line,the_string) <> -1:
            print line

def mygrep(the_string,the_file):
    """ This is usually what I do when I need this. """

    command = 'grep %s %s' % (the_string,the_file)
    response = os.popen(command,'r')
    lines = response.read()
    print lines

if __name__ == '__main__':
    import time

    test_file = "/usr/local/devices/motor.10"
    test_string = "26086594"

    first = time.time()
    pygrep(test_string,test_file)
    second = time.time()
    mygrep(test_string,test_file)
    third = time.time()

    print "Python: %s" % ((second - first),)
    print "OS    : %s" % ((third - second),)

I run this and get:

$ ./pygrep.py
Punc,202,26086594,SG6,1,2,30days,-9,53,732970,358877,0,67,176761,39326,1,24.
94.89.251,

Punc,202,26086594,SG6,1,2,30days,-9,53,751771,371322,0,68,179118,40654,1,24.
94.89.251,

Punc,202,26086594,SG6,1,2,30days,-9,53,787679,393889,0,68,184387,42710,1,24.
94.89.251,

Punc,202,26086594,SG6,1,2,30days,-9,53,732970,358877,0,67,176761,39326,1,24.
94.89.251,
Punc,202,26086594,SG6,1,2,30days,-9,53,751771,371322,0,68,179118,40654,1,24.
94.89.251,
Punc,202,26086594,SG6,1,2,30days,-9,53,787679,393889,0,68,184387,42710,1,24.
94.89.251,

Python: 6.7979799509
OS    : 0.0741490125656

Am I missing a Pydiom that would narrow the gap or is using the OS function
the best way?

-Doug-