text: def caesar(plaintext,shift):
  
  	alphabet=["a","b","c","d","e","f","g","h","i","j","k","l",
  	"m","n","o","p","q","r","s","t","u","v","w","x","y","z"]
  
  	#Create our substitution dictionary
  	dic={}
  	for i in range(0,len(alphabet)):
  		dic[alphabet[i]]=alphabet[(i+shift)%len(alphabet)]
  
  	#Convert each letter of plaintext to the corrsponding
  	#encrypted letter in our dictionary creating the cryptext
  	ciphertext=""
  	for l in plaintext.lower():
  		if l in dic:
  			l=dic[l]
  		ciphertext+=l
  
  	return ciphertext
  
  #Example useage
  plaintext="the cat sat on the mat"
  print "Plaintext:", plaintext
  print "Cipertext:",caesar(plaintext,3)
  #This will result in:
  #Plaintext: the cat sat on the mat
  #Cipertext: wkh fdw vdw rq wkh pdw
  