Python PCEP Tuples and Dictionaries

Tuples and dictionaries
Module 3 Functions, Tuples, Dictionaries,
Data processing

Module 3 Tuples and dictionaries
Sequence types & mutability
sequence types
• is a type of data
• is data which can be scanned by the for loop
2 kinds of Python data
• Mutable data can be freely updated at any time
• Immutable data cannot be modified in this way

What is a tuple?
tuple_1 = (1, 2, 4, 8)
tuple_2 = 1., .5, .25, .125
print(tuple_1)
print(tuple_2)
(1, 2, 4, 8)
(1.0, 0.5, 0.25, 0.125)
create a tuple
empty_tuple = () one_element_tuple_1 = (1, )

Do not modify tuple's contents!
my_tuple = (1, 10, 100,
1000)
print(my_tuple[0])
print(my_tuple[-1])
print(my_tuple[1:])
print(my_tuple[:-2])
for elem in my_tuple:
print(elem)
1
1000
(10, 100, 1000)
(1, 10)
1
10
100
1000
my_tuple = (1, 10, 100,
1000)
my_tuple.append(10000)
del my_tuple[0]
my_tuple[1] = -10
print(my_tuple)
AttributeError: 'tuple' object has no attribute 'append'

How to use a tuple
my_tuple = (1, 10, 100)
t1 = my_tuple + (1000,
10000)
t2 = my_tuple * 3
print(len(t2))
print(t1)
print(t2)
print(10 in my_tuple)
print(-10 not in my_tuple)
9
(1, 10, 100, 1000, 10000)
(1, 10, 100, 1, 10, 100, 1, 10, 100)
True
True
var = 123
t1 = (1, )
t2 = (2, )
t3 = (3, var)
t1, t2, t3 = t2, t3, t1
print(t1, t2, t3)
(2,) (3, 123) (1,)

What is a dictionary?
each key must be unique
a key may be any immutable type of object
a dictionary holds pairs of values
the len() function works for dictionaries
a dictionary is a one-way tool

How to make a dictionary?
dictionary = {"cat": "chat", "dog": "chien", "horse": "cheval"}
phone_numbers = {'boss': 5551234567, 'Suzy': 22657854310}
empty_dictionary = {}
print(dictionary['cat'])
print(phone_numbers['Suzy'])
chat
22657854310
dictionary = {
"cat": "chat",
"dog": "chien",
"horse": "cheval"
}
words = ['cat', 'lion', 'horse']
for word in words:
if word in dictionary:
print(word, "->", dictionary[word])
else:
print(word, "is not in dictionary")
cat -> chat
lion is not in dictionary
horse -> cheval

keys(), sorted()
for key in dictionary.keys():
print(key, "->", dictionary[key])
horse -> cheval
dog -> chien
cat -> chat
for key in sorted(dictionary.keys()):
print(key, "->", dictionary[key])
cat -> chat
dog -> chien
horse -> cheval

items() & values() methods
for english, french in dictionary.items():
print(english, "->", french)
cat -> chat
dog -> chien
horse -> cheval
for french in dictionary.values():
print(french)
cheval
chien
chat

Modifying and adding values
dictionary['cat'] = 'minou'
print(dictionary)
{'cat': 'minou', 'dog': 'chien', 'horse': 'cheval'}
dictionary['swan'] = 'cygne'
print(dictionary)
{'cat': 'chat', 'dog': 'chien', 'horse': 'cheval', 'swan': 'cygne'}

Tuples and dictionaries
• you need a program to evaluate the
students' average scores;
• the program should ask for the student's
name, followed by her/his single score;
• the names may be entered in any order;
• entering an empty name finishes the
inputting of the data;
• a list of all names, together with the
evaluated average score, should be then
emitted.
school_class = {}
while True:
name = input("Enter the student's name: ")
if name == '':
break
score = int(input("Enter the student's score (0-10): "))
if score not in range(0, 11):
break
if name in school_class:
school_class[name] += (score,)
else:
school_class[name] = (score,)
for name in sorted(school_class.keys()):
adding = 0
counter = 0
for score in school_class[name]:
adding += score
counter += 1
print(name, ":", adding / counter)

Key takeaways: tuples
Tuples are ordered and unchangeable (immutable) collections of data.
You can create an empty tuple, one-element tuple.
You can access tuple elements by indexing them.
Tuples are immutable, which means you cannot change their elements
You can loop through a tuple elements .

EXTRA: tuple(), list()
my_tuple = tuple((1, 2, "string"))
print(my_tuple)
my_list = [2, 4, 6]
print(my_list) # outputs: [2, 4, 6]
print(type(my_list)) # outputs: <class 'list'>
tup = tuple(my_list)
print(tup) # outputs: (2, 4, 6)
print(type(tup)) # outputs: <class 'tuple'>
tup = 1, 2, 3,
my_list = list(tup)
print(type(my_list)) # outputs: <class 'list'>

Key takeaways: dictionaries 1
Dictionaries are unordered*, changeable (mutable), and indexed
collections of data.
If you want to access a dictionary item:
pol_eng_dictionary = {"kwiat": "flower","woda": "water","gleba": "soil"}
item_1 = pol_eng_dictionary["gleba"] # ex. 1
print(item_1) # outputs: soil
item_2 = pol_eng_dictionary.get("woda")
print(item_2) # outputs: water

If you want to change the value associated with a specific key:
To add or remove a key (and the associated value):
pol_eng_dictionary["zamek"] = "lock"
item = pol_eng_dictionary["zamek"]
print(item) # outputs: lock
phonebook = {} # an empty dictionary
phonebook["Adam"] = 3456783958 # create/add a key-value pair
print(phonebook) # outputs: {'Adam': 3456783958}
del phonebook["Adam"]
print(phonebook) # outputs: {}

You can use the for loop to loop through a dictionary:
pol_eng_dictionary = {"kwiat": "flower"}
pol_eng_dictionary.update({"gleba": "soil"})
print(pol_eng_dictionary) # outputs: {'kwiat': 'flower', 'gleba': 'soil'}
pol_eng_dictionary.popitem()
print(pol_eng_dictionary) # outputs: {'kwiat': 'flower'}
for item in pol_eng_dictionary:
print(item)
# outputs: zamek
# woda
# gleba

If you want to loop through a dictionary's keys and values:
for key, value in pol_eng_dictionary.items():
print("Pol/Eng ->", key, ":", value)
To check if a given key exists in a dictionary:
if "zamek" in pol_eng_dictionary:
print("Yes")
else:
print("No")

To remove a specific item:
print(len(pol_eng_dictionary)) # outputs: 3
del pol_eng_dictionary["zamek"] # remove an item
pol_eng_dictionary.clear() # removes all the items
del pol_eng_dictionary # removes the dictionary
To copy a dictionary:
copy_dictionary = pol_eng_dictionary.copy()

LAB Practice
29. Tic-Tac-Toe

Congratulations!
You have completed Module 3
the defining and
using of functions
the concept of
passing
arguments in
different ways
name scope
issues
tuples and
dictionaries

Python PCEP Tuples and Dictionaries

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