Python string concatenation performance

A small test revealed that "".join(listOfStrings) is not faster than plain +=. The .join() is slower. Using .append() and .join() is slower.

Time with .join():

real    0m2.908s

Time with +=:

real    0m1.742s

The test:

#!/usr/bin/env python

def combine(inc, count):
    text = ""
    for i in xrange(count):
        text += inc
    return len(text)

def combineByJoin(inc, count):
    text = []
    for i in xrange(count):
        text.append(inc)
    text = "".join(text)
    return len(text)

def main():
    inc = "a" * 10
    print combine(inc, 10000000)
    #print combineByJoin(inc, 10000000)

main()

Tested on Python 2.5.2.

Stop disk clicking

If your disk is clicking on inactivity, it could be because it has too aggressive power management set. Each click will increase Load_Cycle_Count. Check that:

$ sudo smartctl -A /dev/sda | grep Load

To stop it, use hdparm:

$ sudo hdparm -B 254 /dev/sda

See how to force the hdparm setting on boot and resume: https://wiki.ubuntu.com/DanielHahler/Bug59695

Form submit via jQuery

With jQuery it is easy to implement form submit by Ajax. This is how I do it:

$("#filter").submit(function(event) {
    event.preventDefault();
    event.stopPropagation();

    var params = {};
    $(":input", this).each(function() {
      params[this.name] = this.value;
    });

    $.get("/ajax/filter", params, aCallback);
});

A working example is the filter form on Jaký Byt: Mapa.