# Example code for Day 13 Lecture, CS 111 Spring 2014

# Thinking through references
x = 4
y = x
z = x
print x, y, z

y = 7
print x, y, z

x = 8
print x, y, z


# Can't modify arguments!
def addOneToX(x):
    print "In the function, x is", x
    x = x + 1
    print "In the function, after modifying, x is", x

x = 6
print "Before the function call, x is", x
addOneToX(x)
print "After the function call, x is", x


# But lists are mutable!  What are the references now?
P = ["how", "now", "brown", "cow"]
print P
print P[2]

P[2] = "round"
print P

Q = P
print Q

P[1] = "plow"
print P
print Q

Q[3] = "sow"
print P
print Q

P = ["when", "then", "red", "hen"]
print P
print Q


# The *reference* gets passed into a function
def setOneToFive(x):
    print "In the function, x is", x
    x[1] = 5
    print "After modifying, x is", x

L = [7, 8, 9]
print "Before calling the function, L is", L
setOneToFive(L)
print "After calling the function, L is", L



### Dictionaries!

# Creating a dictionary and looking things up in it
phonebook = {}
phonebook['Andre'] = '310-886-1024'
phonebook['Melissa'] = '757-318-2048'
phonebook['Shawn'] = '718-593-4096'

person = "Melissa"
print "%s's number is %s" % (person, phonebook[person])

print type(phonebook)
print phonebook


# Counting words in a big text file

# First we'll make a dictionary mapping each unique word in the text to the
# number of times it occurs.
#   Once you understand this program, try replacing the first line with
# f = open("carroll-alice_s_adventures_in_wonderland.txt", "r")
f = open("alice_tiny.txt", "r")
text = f.read().lower()
f.close()
counts = {}
for token in text.split():
    # Remove any unprintable characters or punctuation at the beginning or end.
    word = token.strip().strip('.!?-\'",;')
    print word
    if len(word) > 0:
        if not counts.has_key(word):
            counts[word] = 1
        else:
            counts[word] += 1

# Now we've populated our dictionary.
# What are the most common words?
top_twenty_words = []
for i in range(20):
    # Find the most common word that we haven't recorded yet.
    max_count = 0
    max_word = ""
    for word in counts.iterkeys():
        if (word not in top_twenty_words) and (counts[word] > max_count):
            max_word = word
            max_count = counts[word]
    # Add the word and its count to our list.
    top_twenty_words.append(max_word)

for word in top_twenty_words:
    print counts[word], word