'''lecture_34_dictionaries.py
Showcase what dictionaries are and how to work with them
Oliver W. Layton
CS 151: Computational Thinking: Visual Media
Fall 2020
'''

'''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 = {}

# 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['grades'])
# print(student['gpa'])


'''Accessing keys and values'''
# You can access the keys and values from the dictionary
# print(student.keys())
# print(student.values())
# You can convert the keys and values into ordinary lists
# keylist = list(student.keys())
# print(keylist[1])
# 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 is', key, '| value is', value)

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

# student['grades'].append(21)
# print(student)

# 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]
# for i in range(len(names)):
#     myDict[names[i]] = gpas[i]
# print(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
# if 'year' in student:
#     print(student['year'])