Random Astronomy Picture of the Day from http://apod.nasa.gov/.

rapod.py

#!/usr/bin/python

#retrieve random Astronomy Picture of the Day
#from http://apod.nasa.gov/

import sys
import datetime
import urllib
import urllib2
import random
import re
from  PIL import Image
import os.path
import json

apodUrl="http://apod.nasa.gov/apod"

def main():
	#TODO: add cli argument to get specifid day
	try:
		today=datetime.date.today()
		earliestDay=datetime.date(1995,6,20)
		day=today
		days=[]
		i=1
		while day>=earliestDay:
			_d=day.strftime("%Y-%m-%d")
			days.append(_d)
			day=today-datetime.timedelta(days=i)
			i=i+1

		chosenDay= random.choice(days)
		#chosenDay="2005-10-01"

		descfname="/tmp/apod%s%s" % (chosenDay,".txt")
		if os.path.isfile(descfname):
			#already exists
			descf=open(descfname,"r")
			ext=""
			for line in descf:
				if line.find("ext=")==-1:
					print line.strip()
				else:
					ext=line.replace("ext=","").strip()
			descf.close()
			fname="/tmp/apod%s%s" % (chosenDay,ext)
			img = Image.open(fname)
			img.show()
			sys.exit(0)

		apodDay=chosenDay[2:].replace("-","")
		url="%s/ap%s.html" % (apodUrl,apodDay)

		descf=open(descfname,"w")
		out="Chosen day: %s" % chosenDay
		print out
		descf.write(out+"\n")
		out= "URL       : %s" % url
		print out
		descf.write(out+"\n")

		apodHtml=urllib2.urlopen(url).read()
		imageUrl=getImageUrl(apodHtml)
		nameandcredits=getImageNameAndCredits(apodHtml)	
		rx=re.compile(r'<[^>]+>')
  		nameandcredits = re.sub(rx,'', nameandcredits).strip()	
  		nameandcredits=nameandcredits.split("\n")
  		nc=[]
  		for item in nameandcredits:
  			item=item.strip()
  			if item!="":
  				nc.append(item)
		out= "Image URL : %s" % imageUrl
		print out
		descf.write(out+"\n")
		out=json.dumps(nc,ensure_ascii=False)
		print out
		descf.write(out+"\n")
		ext=imageUrl.rfind(".")
		ext=imageUrl[ext:]
		descf.write("ext="+ext+"\n")
		descf.close()
		fname="/tmp/apod%s%s" % (chosenDay,ext)
		urllib.urlretrieve (imageUrl, fname)
		img = Image.open(fname)
		img.show()

	except Exception as e:
		print "ERROR: ",e
		sys.exit(1)

def getImageUrl(html):
	htmlL=html.lower()
	index=htmlL.find("<img")
	if index==-1:
		raise Exception("Image not found")

	endIndex=htmlL.find(">",index)
	imgSrc=html[index:endIndex]
	imgStart=imgSrc.find('"')+1
	imgEnd=imgSrc.find('"',imgStart)
	imgSrc=imgSrc[imgStart:imgEnd]
	return "%s/%s" % (apodUrl,imgSrc)

def getImageNameAndCredits(html):
	#print html
	htmlL=html.lower()
	index=htmlL.find("<img")
	endIndex=htmlL.find("</a>",index)
	endIndex=htmlL.find("explanation",endIndex)
	nameandcredits=html[index:endIndex]
	return nameandcredits

if __name__ == "__main__": 
	main()