1. ascii_dictionary.py
2. using_dictionary.py
3. years_dictionary.py

# Demonstrate use of dictionary, using ASCII values
# By Sara Sprenkle

# create an empty dictionary
charToAscii = {}

ordValue = ord('a')

while ordValue <= ord('z'):
    # add mapping to dictionary of chr(ordValue) --> ordValue (ordinal value)
    char = chr(ordValue)
    charToAscii[char] = ordValue
    ordValue += 1

print(charToAscii)
print(sorted(charToAscii))

# demonstrate what happens if you try to look up a value that doesn't exist
print( charToAscii.get('!') )

print( charToAscii['!'] )

print("We don't get to here.")

# Demonstrate use of dictionary using book index
# by Sara Sprenkle

# create an empty dictionary
topicToPageNumber = {}

# add entries to the dictionary
topicToPageNumber["integer"] = 20
topicToPageNumber["list"] = 60
topicToPageNumber["string"] = 35
topicToPageNumber["dictionary"] = 58
topicToPageNumber["float"] = 20


print("~~~~ topicToPageNumber dictionary: ~~~~~~")
# iterates through the keys in the dictionary
for topic in topicToPageNumber:
    # print the key and its associated value
    print(topic, topicToPageNumber[topic])

print()
# display the type that is returned by dictionary methods
print("type of dictionary.keys():", type(topicToPageNumber.keys()))
print("type of dictionary.values():", type(topicToPageNumber.values()))
print("The number of keys is", len(topicToPageNumber.keys()))

# iterate through the values
print("\nIterate through the values:")
for val in topicToPageNumber.values():
    print(val)
    
print("\nLook at the keys:")
keyList = list(topicToPageNumber.keys())
print("as <dict_keys>:\n", topicToPageNumber.keys())
print("as a list:\n", keyList)

print("\nPrint dictionary alphabetically by keys:")
# printing in order by key
keysSorted = list(topicToPageNumber.keys())
keysSorted.sort()

for topic in keysSorted:
    # print the key and its associated value
    print(topic, topicToPageNumber[topic])

print("\nPrint dictionary alphabetically by keys, again, in a different way:")

for topic in sorted(topicToPageNumber):
    print(topic, topicToPageNumber[topic])

print("\nWhat happens if you try to access a key that doesn't exist?")
# demonstrate what happens if you try to look up a value that doesn't exist
print( "Using get:", topicToPageNumber.get('anothertopic') )

print( "Using indexing:",  topicToPageNumber['anothertopic'] )

# Given a file of the form <firstname> <class>
# creates a mapping between the first names and class
# (In progress...)
# by CSCI 111

FILENAME="data/roster.dat"

# open the file for reading
yearsFile = open(FILENAME, "r")

nameToGradYear = {}
# for each line in the file
for line in yearsFile:
    # split the line into the two elements
    nameAndGradYearList = line.split()
    name = nameAndGradYearList[0]
    gradYear = nameAndGradYearList[1]
    # add the student name as the key and the grad year as the value
    nameToGradYear[name] = gradYear
    
print(nameToGradYear)

print("This program will repeatedly prompt you for a")
print("student's first name and tell you their graduation year.")
print("It stops if you enter nothing for a name.")

#repeatedly (until the user enters nothing)
while True:
    # prompt for the student name and display their class year
    studentName = input("What is the student's name? ")
    
    if studentName == "":
        break