Chapter 3: Tuples, Lists, and Dictionaries¶

In this chapter, we will explore three fundamental data structures in Python: Tuples, Lists, and Dictionaries. Understanding these structures is crucial for data organization, storage, and manipulation in Python programming.

1. Tuples¶

Tuples are immutable sequences, typically used to store collections of heterogeneous data. Tuples are defined by enclosing the elements in parentheses ().

1.1 Creating a Tuple¶

To create a tuple, you simply list the values within parentheses, separated by commas.

In [1]:

# A tuple of integers
my_tuple = (1, 2, 3)

# A tuple with mixed data types
mixed_tuple = ("Hello", 100, 1.5)

# A tuple of integers my_tuple = (1, 2, 3) # A tuple with mixed data types mixed_tuple = ("Hello", 100, 1.5)

1.2 Accessing Tuple Elements using index¶

You can access elements of a tuple by using indexing, with the first element at index 0.

In [2]:

print(my_tuple[0])  # Output: 1
print(mixed_tuple[1])  # Output: 100

print(my_tuple[0]) # Output: 1 print(mixed_tuple[1]) # Output: 100

1
100

1.3 Sublist (equal to slice())¶

In [4]:

a_tuple = ('crazyit',20,5.6,'fkit',-17)
print(a_tuple[-3:-1])
print(a_tuple[1:-2])
print(a_tuple[::-1])

a_tuple = ('crazyit',20,5.6,'fkit',-17) print(a_tuple[-3:-1]) print(a_tuple[1:-2]) print(a_tuple[::-1])

(5.6, 'fkit')
(20, 5.6)
(-17, 'fkit', 5.6, 20, 'crazyit')

2. Lists¶

Lists are mutable sequences, typically used to store collections of homogeneous items. Lists are defined by enclosing the elements in square brackets [].

2.1 Creating a List¶

To create a list, you place all the items inside square brackets, separated by commas.

In [10]:

# A list of integers
my_list = [1, 2, 3, 4]
print(my_list)
# Adding elements to a list
my_list.append(5)  # my_list is now [1, 2, 3, 4, 5]
print(my_list)

# A list of integers my_list = [1, 2, 3, 4] print(my_list) # Adding elements to a list my_list.append(5) # my_list is now [1, 2, 3, 4, 5] print(my_list)

[1, 2, 3, 4]
[1, 2, 3, 4, 5]

Python lists are also not type-restricted

In [13]:

my_list = [1,2,3,'a']
print(my_list)

my_list = [42, "hello", 3.14, [1, 2, 3], {'key': 'value'}, True]

print(my_list)

my_list = [1,2,3,'a'] print(my_list) my_list = [42, "hello", 3.14, [1, 2, 3], {'key': 'value'}, True] print(my_list)

[1, 2, 3, 'a']
[42, 'hello', 3.14, [1, 2, 3], {'key': 'value'}, True]

2.2 Add elements to list¶

• append(): Adds a single element to the end of the list.
  • my_list.append(element)
• extend(): Adds elements from an iterable (e.g., list, tuple, string) to the end of the list.
  • my_list.extend([element1, element2])
• insert(): Inserts a given element at a specified position in the list.
  • my_list.insert(index, element)

In [21]:

a_list = ['crazyit',20,-2]
a_list.append('fkit')
print(a_list)

a_list = ['crazyit',20,-2] a_list.append('fkit') print(a_list)

['crazyit', 20, -2, 'fkit']

In [23]:

a_list.append(['a','b'])
print(a_list)
a_list.append(('a','b'))
print(a_list)

a_list.append(['a','b']) print(a_list) a_list.append(('a','b')) print(a_list)

['crazyit', 20, -2, 'fkit', ['a', 'b'], ['a', 'b']]
['crazyit', 20, -2, 'fkit', ['a', 'b'], ['a', 'b'], ('a', 'b')]

In [26]:

b_list = ['a',30]
b_list.extend((-2,3.1))
print(b_list)

b_list = ['a',30]
b_list =  b_list + [-2,3.1]
print(b_list)

b_list = ['a',30] b_list.extend((-2,3.1)) print(b_list) b_list = ['a',30] b_list = b_list + [-2,3.1] print(b_list)

['a', 30, -2, 3.1]
['a', 30, -2, 3.1]

In [27]:

b_list = ['a',30]
b_list =  b_list + (-2,3.1)
print(b_list)

b_list = ['a',30] b_list = b_list + (-2,3.1) print(b_list)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[27], line 2
      1 b_list = ['a',30]
----> 2 b_list =  b_list + (-2,3.1)
      3 print(b_list)

TypeError: can only concatenate list (not "tuple") to list

In [28]:

c_list = list(range(1,6))
print(c_list)
c_list.insert(3,'CRAZY')
print(c_list)

c_list = list(range(1,6)) print(c_list) c_list.insert(3,'CRAZY') print(c_list)

[1, 2, 3, 4, 5]
[1, 2, 3, 'CRAZY', 4, 5]

In [29]:

c_list.insert(3,tuple('crazy'))
print(c_list)

c_list.insert(3,tuple('crazy')) print(c_list)

[1, 2, 3, ('c', 'r', 'a', 'z', 'y'), 'CRAZY', 4, 5]

2.3 Remove elements from List¶

del statement: This is not a function but a Python statement. It removes an item at a specific index or slices of elements from the list. It can also delete the list entirely.

In [30]:

my_list = ['a', 'b', 'c', 'd']
del my_list[1]  # Removes 'b'
# Result: ['a', 'c', 'd']
print(my_list)

my_list = ['a', 'b', 'c', 'd'] del my_list[1] # Removes 'b' # Result: ['a', 'c', 'd'] print(my_list)

['a', 'c', 'd']

remove() method: Removes the first occurrence of a value without needing to know its index. If the item is not found, it raises a ValueError.

In [31]:

my_list = ['apple', 'banana', 'cherry']
my_list.remove('banana')  # Removes 'banana'
# Result: ['apple', 'cherry']
print(my_list)

my_list = ['apple', 'banana', 'cherry'] my_list.remove('banana') # Removes 'banana' # Result: ['apple', 'cherry'] print(my_list)

['apple', 'cherry']

pop() method: Removes and returns an item at a given index (default is the last item). Without an argument, it removes the last item in the list.

In [32]:

my_list = [10, 20, 30, 40, 50]
removed_item = my_list.pop(2)  # Removes 30
# Result: [10, 20, 40, 50], removed_item = 30
print(my_list)

my_list = [10, 20, 30, 40, 50] removed_item = my_list.pop(2) # Removes 30 # Result: [10, 20, 40, 50], removed_item = 30 print(my_list)

[10, 20, 40, 50]

clear() method: Empties the list, removing all items. The list remains, but it will have no content.

In [33]:

my_list = [1, 2, 3, 4, 5]
my_list.clear()  # Clears the list
print(my_list)

my_list = [1, 2, 3, 4, 5] my_list.clear() # Clears the list print(my_list)

[]

2.4 Other Popular Methods¶

• count(): Return number of occurrences of value.
• index(): Return first index of value.
• pop(): Remove and return item at index (default last). [Using list as Stack]
• reverse(): Reverse the elements in a list
• sort(): Sort the elements in a list

In [34]:

a_list = [2,30,'a',[5,30],30]
print(a_list.count(30))
print(a_list.count([5,30]))

a_list = [2,30,'a',[5,30],30] print(a_list.count(30)) print(a_list.count([5,30]))

2
1

In [35]:

a_list = [2,30,'a','b','crazyit',30]
print(a_list.index(30))

a_list = [2,30,'a','b','crazyit',30] print(a_list.index(30))

1

Search start from index 2

In [36]:

print(a_list.index(30,2))

print(a_list.index(30,2))

5

In [37]:

print(a_list.index(30,2,4))

print(a_list.index(30,2,4))

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Cell In[37], line 1
----> 1 print(a_list.index(30,2,4))

ValueError: 30 is not in list

Search start of index from 2 to 4

In [38]:

a_list = list(range(1,8))
a_list.reverse()
print(a_list)

a_list = list(range(1,8)) a_list.reverse() print(a_list)

[7, 6, 5, 4, 3, 2, 1]

In [39]:

a_list = [3,4,-2,-30,14,9.3,3.4]
a_list.sort()
print(a_list)

a_list = [3,4,-2,-30,14,9.3,3.4] a_list.sort() print(a_list)

[-30, -2, 3, 3.4, 4, 9.3, 14]

In [40]:

b_list = ['Python','Swift','Ruby','Go','Kotlin','Erlang']
b_list.sort()
print(b_list)

b_list = ['Python','Swift','Ruby','Go','Kotlin','Erlang'] b_list.sort() print(b_list)

['Erlang', 'Go', 'Kotlin', 'Python', 'Ruby', 'Swift']

Sort by given key func

In [42]:

b_list.sort(key = len)
print(b_list)
b_list.sort(key = len, reverse= True)
b_list

b_list.sort(key = len) print(b_list) b_list.sort(key = len, reverse= True) b_list

['Go', 'Ruby', 'Swift', 'Erlang', 'Kotlin', 'Python']

Out[42]:

['Erlang', 'Kotlin', 'Python', 'Swift', 'Ruby', 'Go']

3. Shared property / methods of Tuple and List¶

3.1 Addition¶

In [5]:

a_tuple = ('crazyit',20,-1.2)
b_tuple = (127,'crazyit','fkit',3.33)
sum_tuple = a_tuple + b_tuple
print(sum_tuple)
print(a_tuple)
print(b_tuple)

a_tuple = ('crazyit',20,-1.2) b_tuple = (127,'crazyit','fkit',3.33) sum_tuple = a_tuple + b_tuple print(sum_tuple) print(a_tuple) print(b_tuple)

('crazyit', 20, -1.2, 127, 'crazyit', 'fkit', 3.33)
('crazyit', 20, -1.2)
(127, 'crazyit', 'fkit', 3.33)

In [6]:

print(a_tuple + (-20,-30))

print(a_tuple + (-20,-30))

('crazyit', 20, -1.2, -20, -30)

In [14]:

a_list = [20,30,50,100]
b_list = ['a','b','c']
sum_list = a_list + b_list
print(sum_list)
print(a_list + ['fkit'])

a_list = [20,30,50,100] b_list = ['a','b','c'] sum_list = a_list + b_list print(sum_list) print(a_list + ['fkit'])

[20, 30, 50, 100, 'a', 'b', 'c']
[20, 30, 50, 100, 'fkit']

3.2 Multiply¶

In [7]:

mul_tuple = a_tuple * 3
print(mul_tuple)

mul_tuple = a_tuple * 3 print(mul_tuple)

('crazyit', 20, -1.2, 'crazyit', 20, -1.2, 'crazyit', 20, -1.2)

In [15]:

a_list = [30,'Python',2]
mul_list = a_list * 3
print(mul_list)

a_list = [30,'Python',2] mul_list = a_list * 3 print(mul_list)

[30, 'Python', 2, 30, 'Python', 2, 30, 'Python', 2]

Example for adding ending of date

In [16]:

order_endings = ('st','nd','rd')\
    + ('th',) * 17 + ('st','nd','rd')\
    + ('th',) * 7 + ('st',)
print(order_endings)

order_endings = ('st','nd','rd')\ + ('th',) * 17 + ('st','nd','rd')\ + ('th',) * 7 + ('st',) print(order_endings)

('st', 'nd', 'rd', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'st', 'nd', 'rd', 'th', 'th', 'th', 'th', 'th', 'th', 'th', 'st')

In [17]:

day = input("please enter a date(1-31)")
day_int = int(day)
print(day + order_endings[day_int -1])

day = input("please enter a date(1-31)") day_int = int(day) print(day + order_endings[day_int -1])

28th

3.3 Query elements use in¶

In [18]:

a_tuple = ('crazyit',20,-1.2)
print(20 in a_tuple)
print(1.2 in a_tuple)
print('fkit' not in a_tuple)

a_tuple = ('crazyit',20,-1.2) print(20 in a_tuple) print(1.2 in a_tuple) print('fkit' not in a_tuple)

True
False
True

3.4 Statistics¶

• len()
• max()
• min()

In [19]:

a_tuple = (20,10,-2,15.2,102,50)
print(max(a_tuple))
print(min(a_tuple))
print(len(a_tuple))

a_tuple = (20,10,-2,15.2,102,50) print(max(a_tuple)) print(min(a_tuple)) print(len(a_tuple))

102
-2
6

In [20]:

b_list = ['crazyit','fkit','Python','Kotlin']
print(max(b_list))
print(min(b_list))
print(len(b_list))

b_list = ['crazyit','fkit','Python','Kotlin'] print(max(b_list)) print(min(b_list)) print(len(b_list))

fkit
Kotlin
4

4. Dictionaries¶

Dictionaries are mutable data types that store mappings of unique keys to values. Dictionaries are defined by enclosing key-value pairs in curly braces {}

4.1 Creating a Dictionary¶

To create a dictionary, you use curly braces with key-value pairs separated by colons.

In [44]:

# A simple dictionary
my_dict = {"name": "Alice", "age": 25}
print(my_dict)

# Adding a new key-value pair
my_dict["city"] = "New York"  # my_dict now includes "city": "New York"
print(my_dict)

# A simple dictionary my_dict = {"name": "Alice", "age": 25} print(my_dict) # Adding a new key-value pair my_dict["city"] = "New York" # my_dict now includes "city": "New York" print(my_dict)

{'name': 'Alice', 'age': 25}
{'name': 'Alice', 'age': 25, 'city': 'New York'}

Key could be tuple but not list!

In [46]:

dict2 = {(20,30):'good',30:'bad'}
print(dict2)
# dict2 = {[20,30]:'good',30:'bad'}
# print(dict2)

dict2 = {(20,30):'good',30:'bad'} print(dict2) # dict2 = {[20,30]:'good',30:'bad'} # print(dict2)

{(20, 30): 'good', 30: 'bad'}

Transfer List to Dictionary

In [47]:

vegetables = [('celery',1.58),('brocoli',1.29),('lettuce',2.19)]
dict3 = dict(vegetables)
print(dict3)

vegetables = [('celery',1.58),('brocoli',1.29),('lettuce',2.19)] dict3 = dict(vegetables) print(dict3)

{'celery': 1.58, 'brocoli': 1.29, 'lettuce': 2.19}

In [48]:

cars = [['BMW',8.5],['BENS',8.3],['AUDI',7.9]]
dict4 = dict(cars)
print(dict4)

cars = [['BMW',8.5],['BENS',8.3],['AUDI',7.9]] dict4 = dict(cars) print(dict4)

{'BMW': 8.5, 'BENS': 8.3, 'AUDI': 7.9}

4.2 Basic Usage of Dictionary¶

• Use key to access value
• Use key to add key-value record
• Use key to delete key-value record
• Use key to modify key-value record
• Use key to search key-value

In [49]:

scores = {'literature':89, 'Math': 92, 'English': 93}
print(scores['Math'])

scores = {'literature':89, 'Math': 92, 'English': 93} print(scores['Math'])

92

In [50]:

del scores['English']
print(scores)

del scores['English'] print(scores)

{'literature': 89, 'Math': 92}

In [51]:

print('literature' in scores)
print('gym' not in scores)

print('literature' in scores) print('gym' not in scores)

True
True

4.3 Useful functions¶

clear()

In [52]:

cars

cars

Out[52]:

[['BMW', 8.5], ['BENS', 8.3], ['AUDI', 7.9]]

In [53]:

cars.clear()
print(cars)

cars.clear() print(cars)

[]

get(): get values based on key

In [54]:

print(scores.get('Math'))
print(scores.get('gym'))

print(scores.get('Math')) print(scores.get('gym'))

92
None

update()

In [55]:

print(scores)
scores.update({'History':89, 'English':91})
print(scores)

print(scores) scores.update({'History':89, 'English':91}) print(scores)

{'literature': 89, 'Math': 92}
{'literature': 89, 'Math': 92, 'History': 89, 'English': 91}

• items(): get all key-value record
• keys(): get all keys
• values(): get all values

In [56]:

subjects = scores.items()
print(subjects)
print(type(subjects))

subjects = scores.items() print(subjects) print(type(subjects))

dict_items([('literature', 89), ('Math', 92), ('History', 89), ('English', 91)])
<class 'dict_items'>

In [57]:

kys = scores.keys()
print(type(kys))
print(kys)

kys = scores.keys() print(type(kys)) print(kys)

<class 'dict_keys'>
dict_keys(['literature', 'Math', 'History', 'English'])

In [58]:

vals = scores.values()
print(type(vals))
print(vals)

vals = scores.values() print(type(vals)) print(vals)

<class 'dict_values'>
dict_values([89, 92, 89, 91])

pop() and popitem()

In [59]:

print(scores)
print(scores.pop('English'))
print(scores)

print(scores) print(scores.pop('English')) print(scores)

{'literature': 89, 'Math': 92, 'History': 89, 'English': 91}
91
{'literature': 89, 'Math': 92, 'History': 89}

In [60]:

print(scores.popitem())
print(scores)

print(scores.popitem()) print(scores)

('History', 89)
{'literature': 89, 'Math': 92}

In [61]:

k,v = scores.popitem()
print(k,v)

k,v = scores.popitem() print(k,v)

Math 92

4.3 setdefault() and fromkeys()¶

• setdefault() Return the value of given key, if given key not exist in the origin dictionary, would return the given value.
• fromkeys() Create dictionary from given list, using the elements from list as keys

In [62]:

cars = {'BMW':8.5, 'BENS':8.3, 'AUDI':7.9}
print(cars.setdefault('PORSCHE',9.2))
print(cars)

cars = {'BMW':8.5, 'BENS':8.3, 'AUDI':7.9} print(cars.setdefault('PORSCHE',9.2)) print(cars)

9.2
{'BMW': 8.5, 'BENS': 8.3, 'AUDI': 7.9, 'PORSCHE': 9.2}

In [63]:

print(cars.setdefault('BENS',5.2))
print(cars)

print(cars.setdefault('BENS',5.2)) print(cars)

8.3
{'BMW': 8.5, 'BENS': 8.3, 'AUDI': 7.9, 'PORSCHE': 9.2}

In [64]:

a_dict = dict.fromkeys(['a','b'])
print(a_dict)

a_dict = dict.fromkeys(['a','b']) print(a_dict)

{'a': None, 'b': None}

In [65]:

b_dict = dict.fromkeys((13,17))
print(b_dict)

b_dict = dict.fromkeys((13,17)) print(b_dict)

{13: None, 17: None}

In [66]:

c_dict = dict.fromkeys((13,17),'good')
print(c_dict)

c_dict = dict.fromkeys((13,17),'good') print(c_dict)

{13: 'good', 17: 'good'}

4.4 Using dictionary to format string¶

In [67]:

temp = 'book name is %(name)s, price is %(price)06.2f, published by %(publish)s'
book = {'name':'Crazy Python','price':78.9,'publish':'who cares'}
print(temp % book)

temp = 'book name is %(name)s, price is %(price)06.2f, published by %(publish)s' book = {'name':'Crazy Python','price':78.9,'publish':'who cares'} print(temp % book)

book name is Crazy Python, price is 078.90, published by who cares

In [68]:

book = {'name':'Crazy JAVA','price':88.9,'publish':'I do not know'}
print(temp % book)

book = {'name':'Crazy JAVA','price':88.9,'publish':'I do not know'} print(temp % book)

book name is Crazy JAVA, price is 088.90, published by I do not know