Handling huge data - Python example

File Handling example from a Well House Consultants training course
More on File Handling [link]

This example is described in the following article(s):
• Python - fresh examples from recent courses - [link]

Source code: majorcooker.py Module: Y110

""" Handling huge data

Here's a program that reads 30 log files totalling over 1Gbyte of data - that's
over 4 million lines of web server logs - and filters them for lines containing
"Melksham". On an Apple laptop (MacBook Pro) this program took just under 5 seconds
to run.

Note the use of xreadlines to keep the memory profile low - lines are only read in
as they're needed, rather than reading in the whole of an input file in to a huge
list! """

import os
import time

def getplace(where):
        global overall
        fyles = os.listdir(".")
        for fyle in fyles:
                if fyle.startswith("ac_201011"):
                        for line in open(fyle).xreadlines():
                                overall += 1
                                if line.find(where) > -1:
                                        # print "Found one"
                                        yield line

matched = 0
overall = 0
started = time.time()
for access in getplace("Melksham"):
        bits = access.split(" ")
        # print bits[0],bits[6]
        matched += 1
finished = time.time()

print "matches =",matched,"of",overall
print "elapsed time: ",finished - started

""" Output:

wizard:pyoo graham$ python majorcooker.py
matches = 32678 of 4212183
elapsed time: 4.60196805
wizard:pyoo graham$

"""

Learn about this subject

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* Learning to program in Python
* Python Programming
Also available on on site courses for larger groups

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