'''lecture_24_dictionaries.py
Showcase what dictionaries are and how to work with them
Oliver W. Layton
CS 151: Computational Thinking: Visual Media
Spring 2021
'''

'''Dictionaries
Works like a physical dictionary or address book:
    you look up a definition ("value") using a WORD ("key")
Different from a list where you look up a value using an INDEX.
'''
# Make a new empty dictionary
myDict = {}
# print(myDict)

# Make a new dictionary with some initial data
# Words (keys): 'grades', 'gpa', 'school'
# Definitions (values): [26, 27, 26], 3.8, 'Colby'
student = {'grades': [26, 27, 26], 'gpa': 3.8, 'school': 'Colby'}
# print(student)
# print('The student\'s grades are:', student['grades'])

'''Accessing keys and values'''
# You can access the keys and values from the dictionary
theKeys = student.keys()
# print(theKeys)

theValues = student.values()
# print(theValues)

# You can convert the keys and values into ordinary lists
keyList = list(student.keys())
# print(keyList)
# print(keyList[0])

valueList = list(student.values())
# print(valueList)

# You can loop through keys or values (without converting to lists first)
# Example, loop through keys and values, append each to a list
keys = []
values = []

# for key in student.keys():
#     keys.append(key)
# print(keys)

# for value in student.values():
#     values.append(value)
# print(values)


# You can loop through both at the same time using the items method
# for key, value in student.items():
#     print('Key:', key, '| value:', value)

'''Modifying/adding to a dictionary'''
# Examples: set school to Colby College, add a grade, add a key for dorm
print(student)
student['school'] = 'Colby College'
# print(student)

# student['grades'] = [26, 27, 26, 30]
student['grades'].append(30)


student['dorm'] = 'Taylor'
print(student)

'''Adding to a dictionary via string variables'''
# Example: names-to-GPA lists:
names = ['Bill', 'Carol', 'Ben']
gpas = [4, 3.8, 3.6]
myDict = {}
for i in range(len(names)):
    myDict[names[i]] = gpas[i]
print('Dictionary:', myDict)

'''Checking if a key is in the dictionary'''
# Program will crash if you try to access a key that doesn't exist, so it is a good idea to check
# for it before accessing
# myDict['hi'] = 'there'
if 'hi' in myDict:
    print(myDict['hi'])
else:
    print('its not in there.')