PDA_note_week1.py

"""
Python Data Analysis
WEEK ONE

Course Note and Quiz 
"""


"""
Dictionary creation.
"""

print("Dictionary Literals")
print("===================")

# Dictionary literals
empty = {}
print(empty)

simple = {1: 2}
print(simple)

squares = {1: 1, 2: 4, 3: 9, 4: 16}
print(squares)

cipher = {'p': 'o', 'y': 'h', 't': 'n',
          'h': 't', 'o': 'y', 'n': 'p'} 
print(cipher)

goodinstructors = {'Rixner': True, 'Warren': False}
print(goodinstructors)

cities = {'China': ['Shanghai', 'Beijing'],
          'USA': ['New York', 'Los Angeles'],
          'Spain': ['Madrid', 'Barcelona'],
          'Australia': ['Sydney', 'Melbourne'],
          'Texas': ['Houston', 'San Antonio']}
print(cities)

print("")
print("Creating Dictionaries")
print("=====================")

empty2 = dict()
print(empty2)

data = [(1, 'one'), (2, 'two'), (3, 'three')]
names = dict(data)
print(names)

cipher2 = dict(cipher)
print(cipher2)

"""
Dictionary lookup and update.
"""


print("Dictionary Lookup")
print("=================")

cipher = {'p': 'o', 'y': 'h', 't': 'n',
          'h': 't', 'o': 'y', 'n': 'p'} 
print(cipher)

# Use indexing with keys to access values
print(cipher['t'])
print(cipher['n'])

def encrypt(cipher, word):
    """encrypt word using cipher"""
    encrypted = ""
    for char in word:
        encrypted += cipher[char]
    return encrypted

python = "python"
enc = encrypt(cipher, python)
print(python, enc)

# It is an error to use a non-existent key
# print(cipher[1])

# Use .get when you are unsure if the key exists
print(cipher.get('t'))
print(cipher.get(1))
print(cipher.get(1, 'z'))

print("")
print("Dictionary Update")
print("=================")

print(cipher)

# Modify an existing key->value mapping
cipher['p'] = 'q'
print(cipher)

# Create a new key->value mapping
cipher['r'] = 'z'
print(cipher)

enc2 = encrypt(cipher, python)
print(python, enc, enc2)

"""
Checking for keys in a dictionary.
"""

print("Using 'in'")
print("==========")

mapping = {1: 5, 8: -3, 7: 22, 4: 13, 22: 17}

# Keys
print(1 in mapping)
print(8 in mapping)

# Values
print(5 in mapping)
print(-3 in mapping)

# Both
print(22 in mapping)

# Neither
print(82 in mapping)

print("")

print("Protecting from Errors")
print("======================")

keys = [8, 14, 22, 25]

#for key in keys:
#    print(key, mapping[key])

for key in keys:
    if key in mapping:
        print(key, mapping[key])
    else:
        print("{} not in mapping".format(key))


print("Issues with Keys")
print("================")
        
# Be careful with what you use as keys!
# If all keys are of the same type, you won't run
#  into these issues
mapping = {4.0: 2, 'a': 3, True: 'true', False: 9}
print(mapping)

mapping[1] = 7
print(mapping)

mapping[0] = 'false'
print(mapping)

mapping[4] = 7
print(mapping)

mapping['A'] = 'abc'
print(mapping)

print("Week 1 Quiz")
print("================")

q3_dict = {1: 2, 3: 4}
print(1 in q3_dict)

def count_letters(word_list):
    """ 
    Input: a list of words that are composed entirely of lower case letters 
    Return: the lower case letter that appears most frequently 
      (total number of occurrences) in the words in 𝚠𝚘𝚛𝚍_𝚕𝚒𝚜𝚝.

    In the case of ties, return the earliest letter in alphabetical order
    """
    
    ALPHABET = "abcdefghijklmnopqrstuvwxyz"

    letter_count = {}
    for letter in ALPHABET:
        letter_count[letter] = 0
        
    # enter code here
    for word in word_list:
        letters = list(word)
        for letter in letters:
            if letter in ALPHABET:
                letter_count[letter] += 1
        


    max_count = 0
    max_letter = ''

    for key, value in letter_count.items():
        if letter_count[key] > max_count:
            max_count = value
            max_letter = key
     
    return max_letter

print(count_letters(["hello", "world"]))

monty_quote = "listen strange women lying in ponds distributing swords is no basis for a system of government supreme executive power derives from a mandate from the masses not from some farcical aquatic ceremony"
monty_words = monty_quote.split(" ")

print(count_letters(monty_words))