Python - a simple polymorphism example

# A quick example of polymorphism at work in python 
 
class Food(object):
    def __init__(self, name, calories):
        self.name = name
        self.calories = calories
    def tastesLike(self):
        raise NotImplementedException("Subclasses are responsible for creating this method")
 
class HotDog(Food):
    def tastesLike(self):
        return "Extremely processed meat" 
 
class Hamburger(Food):
    def tastesLike(self):
        return "grilled goodness" 
 
class ChickenPatty(Food):
    def tastesLike(self):
        return "tastes like chicken" 
 
dinner = []
dinner.append(HotDog('Beef/Turkey BallPark', 230))
dinner.append(Hamburger('Lowfat Beef Patty', 260))
dinner.append(ChickenPatty('Micky Mouse shaped Chicken Tenders', 170))
 
# even though each course of the dinner is a differnet type 
# we can process them all in the same loop 
for course in dinner:
    print course.name + " is type " + str(type(course))
    print "  has " + str(course.calories) + " calories " 
    print "  and tastes like " + course.tastesLike()
 
 
# my output: 
# 
#Beef/Turkey BallPark is type <class '__main__.HotDog'> 
#  has 230 calories 
#  and tastes like Extremely processed meat 
#Lowfat Beef Patty is type <class '__main__.Hamburger'> 
#  has 260 calories 
#  and tastes like grilled goodness 
#Micky Mouse shaped Chicken Tenders is type <class '__main__.ChickenPatty'> 
#  has 170 calories 
#  and tastes like tastes like chicken 
 
 

Python - determine an image's type (regardless of extension)

# iterate through all the files in the current directory
# identify the type of image file (regardless of extension)


import os
import imghdr


# list files in the current working directory 

for f in os.listdir('.'):
    if os.path.isfile(f):
        imgtype = imghdr.what(f)
        if imgtype is None:
            imgtype = "not image"

    print "'" + f + "'" + " is type " + imgtype



#output: (for me)

#'2007 Oct 31 146.jpg' is type jpeg

#
#'2007 Oct 31 147.jpg' is type jpeg
#
#'2007 Oct 31 148.jpg' is type jpeg
#
#'2007 Oct 31 149.image' is type jpeg

#
#'2007 Oct 31 150.jpg' is type jpeg
#
#'big kitty.GI' is type gif
#
#'eric.image' is type jpeg

#
#'LICENSE.txt' is type not image
#
#'NEWS.txt' is type not image
#