CPU Usage in Python

#!/usr/bin/env python

import time
import sys

def collect( ):
    result = { }
    fd = open( "/proc/stat" )
    while True:
        data = fd.readline( )
        if data == '': break
        if not data.startswith( "cpu" ): continue
        key, delimiter, data = data.partition( " " )
        result[ key ] = [ float( x ) for x in data.rstrip( ).split( ) ]
    fd.close( )
    return result

def process( first, second ):
    result = { }
    for key in first:
        a = first[ key ]
        b = second[ key ]
        v1 = b[ 0 ] - a[ 0 ] + b[ 2 ] - a[ 2 ]
        v2 = v1 + b[ 3 ] - a[ 3 ]
        result[ key ] = 0
        if v2 > 0:
            result[ key ] = ( v1 * 100.0 ) / v2
    return result

first = collect( )
while True:
    time.sleep( 0.1 )
    second = collect( )
    result = process( first, second )
    for key in sorted( result.keys( ) ):
        print result[ key ],
    print
    sys.stdout.flush( )
    first = second