hourly frequency plot using python matplotlib

gistfile1.py

#!/usr/bin/env python
import numpy as np
import matplotlib.mlab as mlab
import matplotlib.pyplot as plt

from datetime import datetime, tzinfo, timedelta

# a class to implement abstract tzinfo
class Zone(tzinfo):
    def __init__(self, offset, isdst, name):
        self.offset = offset
        self.isdst = isdst
        self.name = name
    def utcoffset(self, dt):
        return timedelta(hours=self.offset) + self.dst(dt)
    def dst(self, dt):
            return timedelta(hours=1) if self.isdst else timedelta(0)
    def tzname(self, dt):
         return self.name

GMT = Zone(0,False,'GMT')

stamps = []
f = open('epochStamps.txt') # contains seconds since epoch corresponding to an event per line

epochstart = datetime(1970, 1, 1, tzinfo=GMT)
periodstart = datetime(2012, 3, 26, tzinfo=GMT) # lets say data is for 26th march
startstamp = int(timedelta.total_seconds(periodstart - epochstart))

for line in f.readlines():
	stamp = int(line.strip())
	stamps.append(stamp - startstamp) # day start is 0, day end is 86400
f.close()

n, bins, patches = plt.hist(stamps, 24) # hourly bins

plt.show()