Why is Python script reading files much faster the second run?

Question

I read the first line of a couple hundred text files with Python.
This runs under a couple seconds on the first time, but it takes only milliseconds to run the second time!!
Why is that ? Is it python ? Is it the operating system (Windows 7 in my case) ?

Here is the script:

import glob from datetime import datetime start = datetime.now() for summary in glob.glob(r"C:\folder\*.txt"): with open(summary) as f: line = f.readline() print line.rstrip().decode('utf-16') print 'Time: ', datetime.now()-start

phihag · Accepted Answer · 2013-02-12 17:49:18Z

6

That's the disk cache of the operating system.

answered Feb 12, 2013 at 17:49

phihag

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Martijn Pieters · Accepted Answer · 2013-02-12 17:49:21Z

5

It's the operating system. Modern OSes use disk caches to speed up repeated reads.

answered Feb 12, 2013 at 17:49

Martijn Pieters

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Comments

Jon-Eric · Accepted Answer · 2013-02-12 17:49:40Z

Your operating system probably cached the data from disk after the first run. Restart your computer and see how the run time compares.

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