===
10-19-09 Day 13 (though my numbering of the days is off)
=======
Dictionary recap

# Define
emissions = {1799: 1, 1800: 70, 1801: 74, 1802: 82, 1902: 215630, 2002: 1733297}

# Keys can be any immutable object; associated values can be any object
d = {'abc': 32, 7: [1, 2, 3], True: 14.6, ("hi", "friend"): 77}

# Look up
emissions[1802]

# Update
d[4] = "silly"
d[4] = "goofy"
d

# Check length
len(emissions)
len(d)


 - Things you can do with dictionaries:

		# check for membership
		1950 in emissions

		# remove
		>>> del emissions[1950]
		>>> 1950 in emissions
		False

		# loop over a dictionary
		>>> for key in emissions:
		...     print key

		>>> for key in emissions:
		...     print emissions[key]

 - Dictionaries are unordered.  
   The order that the keys are traversed (when you loop through) is arbitrary: 
   there is no guarantee that it will be in the order that they were added.

 - dictionaries are mutable.

== Dictionary methods ==

 - keys
	>>> emissions.keys()
	[1799, 1800, 1801, 1802, 1902, 2002]
 - values
	>>> emissions.values()
	[1, 70, 74, 82, 215630, 1733297]

 - items: the (key, value) pairs
	>>> emissions.items()
	[(1799, 1), (1800, 70), (1801, 74), (1802, 82), (1902, 215630), 
	(2002, 1733297)]
	# this is a list of tuples

 - get
	>>> emissions.get(1802)
	82
	>>> emissions.get(1805) # returns None
	>>> emissions.get(1805, -1)  # return -1 if the key not there.
		-1

 - update: copies values from one dictionary into another
	>>> dict1 = {'978-6025': 'Diane', '978-3965': 'Tom'}
	>>> dict2 = {'978-6360': 'UG office', '978-6025': 'main office'}
	>>> dict1.update(dict2)   # add dict2 contents to dict1
	>>> dict1

 - clear: removes the dictionary contents
	>>> dict2
	>>> dict2.clear()
	>>> dict2


== Phone number example: inverting a dictionary ==

phone = {'555-7632': 'Paul', '555-9832': 'Andrew', '555-6677': 'Jen', '555-9823': 'Michael', '555-6342' : 'Wael', '555-7343' : 'Paul', '555-2222' : 'Michael'}

 - Get all of Paul's phone numbers:

		# Method 1
		>>> paul = []
		>>> for key in phone:
		...     if phone[key] == 'Paul':
		...         paul.append(key)
		... 
		>>> paul
		['555-7632', '555-7343']

 - But what if I want to be able to do this for all people? 
   QU: is there some object you could create to make this easy?

   		- an "inverted" dictionary.
		  The old one takes us from numbers to names.
		  The new one will take us in 
                  the reverse direction, from names to #s

		new_phone = {}
		for (number, name) in phone.items():
		    if name in new_phone:
		       new_phone[name].append(number)
		    else:
		       new_phone[name] = [number]

		>>> new_phone
		{'Jen': ['555-6677'], 'Paul': ['555-7632', '555-7343'], 'Wael': 	
		['555-6342'], 'Michael': ['555-9823', '555-2222'], 'Andrew': ['555-9832']}


[inverted_dict.py] - go through this in the debugger.

==== NOW: we will solve a problem from the beginning.
== Top-down design ==

 - begins at the top level with what you need the program to do 
 - works its way down to functions that the program need
 - then to functions that those functions need, and so on. 

== Writing epics ==

 - We'll develop a program that mimics the writing it has seen
 
 - demo [wannabe.py]

 - Even though the text doesn't make all that much sense, can you see
   the differences in the style?

 - After we understand the code, I'll talk about why this type of
   program is really useful for helping computers to understand human
   language [predict what you will say or type next!]

 
 - QU: How might it work?

(a) Remember what you saw so that you can mimic it

Type "help", "copyright", "credits" or "license" for more information.
>>> # A demo of the program to mimic the writing in a text:
>>> Evaluating epic.py
 upon the sky, So shall behold the humble-bees, And leads me come to be not this cold fruitless moon. TITANIA. Thou shalt buy this advantage take, An I have we grew together, More than arrow from my Thisby's face. Where art thou aby it. What though I pick'd a day As Shafalus to be a fine tragedy. And here together. THESEUS. True; and you were a little voice: 'Thisne, Thisne!' [Then speaking small] 'Ah Pyramus, I'll apply To greet me like to steal. HERMIA. Methinks she was in love you? HELENA. Your vows are to perish on thee! [They sleep] Enter OBERON at the Duke of doubt he That is too old device, and here's a day. The lover, that from his scene of Athens here, But, in the wood Enter DEMETRIUS I'll give a girdle round and lovers seek new ribbons to entreat your patience well. Exit Enter a woman, God warrant us: She shall we come without warning. HIPPOLYTA. How can be set aside. Away with thy brawls thou aby it. Demetrius loves me have a serpent. HERMIA. I see. Dian's bud o'er and not merit. Where is a knavery of man to form in mockery, set. The
>>>
>>> # The kind of dictionary we want to build:
    # for midsummernight.txt  
>>> d = {"happy": ["days", "is", "fair!", "some", "is", "hour!"]}
>>> d["couples"] = ["shall","three"]
>>> d
[Go into midsummernight.txt to find these occurences of the words]
>>>
>>> # To mimic the writing we've read: suppose we just wrote word w.
>>> # Now, random pick the next word from the list of follow-on words for w in
>>> # our dictionary.  Separate issue: what word to start the whole thing with.
>>>
>>> # How to pick a random element of a list:
>>> inport random
>>> 
>>> l = [5,2,7,33,1,2,66,5]  
>>> random.shuffle(l)
>>> l
[2, 66, 2, 1, 33, 7, 5, 5]
>>> random.shuffle(l)
>>> l
[1, 5, 2, 2, 5, 33, 66, 7]
Remember d?
d