python tips: create line graph with matplotlib

*** sample code (mypg.py) ***

#/usr/bin/env python                                                       
# coding:utf-8                                                             

# need to install python-pygresql                                          
import pg
import sys
from pylab import *

def main():
argvs = sys.argv
argc = len(argvs)

# check argument                                                       
if (argc != 4):
   print "Usage: python %s dbname dbuser dbpass" % (argvs[0])
   sys.exit(1)

dbname=argvs[1]
dbuser=argvs[2]
dbpass=argvs[3]
dbobj = getConnection(dbname, dbuser, dbpass)

# input data from database tables                                      
Lx = getValueX()
L1 = collectData(dbobj, '1')
L2 = collectData(dbobj, '2')
L3 = collectData(dbobj, '3')
L4 = collectData(dbobj, '4')

# plot data using matplotlib                                           
plot(Lx, L1, label='id=1')
plot(Lx, L2, label='id=2')
plot(Lx, L3, label='id=3')
plot(Lx, L4, label='id=4')

# set labels and title                                                 
xlabel('hour')
ylabel('random_value')
title('plot test')

# draw legend                                                          
legend()

# draw graph                                                           
show()

dbobj.close()

def getValueX():
    L = []
    hour = 0
    while (hour <= 23):
        L.append(hour)
        hour += 1
    return L

# collecting data if same id                                                    
def collectData(dbobj, target):
    L = []
    sn = 0
    while sn <= 23:
        dbtable='public.table_' + str(sn)

        sql="SELECT * FROM %s WHERE id = '%s';" % (dbtable, target)
        for row in dbobj.query(sql).dictresult():
            if row['id'] == target:
                L.append(int(row['value']))
        sn += 1

    return L
# debug function                                                                
def showTables(dbobj):
    for tbl in dbobj.get_tables():
        print tbl

# initialize db connection                                                      
def getConnection(dbname, dbuser, dbpass):
    pg.set_defhost('localhost')
    pg.set_defport(5432)
    pg.set_defbase(dbname)
    return pg.DB(user=dbuser, passwd=dbpass)

if __name__ == "__main__":
    main()

*** output from above code ***

yaboo@maniac:~/$ python mypg.py mydb test test

*** matplotlib reference pages ***
ぐうたらの部屋
Matplotlib サンプル集 - Kaiseki
http://www.ike-dyn.ritsumei.ac.jp/~uchida/scipy-lecture-notes/intro/index.html