fasted way to read file in python : I made a python script to analyze logs. I have one observation to share, and two questions to ask. 

When I use gzip.open to open each file and go through every line, it takes around 200 seconds just to going through all the lines and files.

    with gzip.open(file) as fp:
        for line in fp:
If using `zcat` and `grep` to do the work, it takes about 50 seconds.

    temp = commands.getstatusoutput("zcat file* | grep pattern")
The performance difference is too huge to ignore. Is there a better way to reduce the gap?

I also noticed that the `commands` module is made obsolete by the `subprocess` module, which seems always create a temporary file. But it wouldn't be convenient, what if it is not possible to create a temporary file from where the python script is running? Any suggestion?
