Data Structures

🧺 Python’s Data Structures help you organize and manage collections of data efficiently.

1 List (list)

Ordered, mutable (can change data) collections.

prerequisite_courses = ['Intro. to Data Science', 'Data Mining']
print(prerequisite_courses)  # ['Intro. to Data Science', 'Data Mining']

print(type(prerequisite_courses))  # <class 'list'>

prerequisite_courses.append('Data Warehouse')
print(prerequisite_courses)  # ['Intro. to Data Science', 'Data Mining', 'Data Warehouse'] 

print(prerequisite_courses[0])  # 'Intro. to Data Science'

prerequisite_courses[0] = 'Introduction to Data Science'
print(prerequisite_courses)  # ['Introduction to Data Science', 'Data Mining', 'Data Warehouse'] 

['Intro. to Data Science', 'Data Mining']
<class 'list'>
['Intro. to Data Science', 'Data Mining', 'Data Warehouse']
Intro. to Data Science
['Introduction to Data Science', 'Data Mining', 'Data Warehouse']

2 Tuple (tuple)

Ordered, immutable (can not change data) collections.

prerequisite_courses = ('Intro. to Data Science', 'Data Mining')
print(prerequisite_courses)  # ('Intro. to Data Science', 'Data Mining')

print(type(prerequisite_courses))  # <class 'tuple'>

print(prerequisite_courses[0])  # 'Intro. to Data Science']

('Intro. to Data Science', 'Data Mining')
<class 'tuple'>
Intro. to Data Science

3 Set (set)

Unordered collection of unique elements.

prerequisite_courses = {'Introduction to Data Science', 'Data Mining', 'Data Warehouse'}  
print(prerequisite_courses)  # {'Introduction to Data Science', 'Data Mining', 'Data Warehouse'}

print(type(prerequisite_courses))  # <class 'set'>

prerequisite_courses.add('Introduction to Data Science')
print(prerequisite_courses)  # {'Introduction to Data Science', 'Data Mining', 'Data Warehouse'}

{'Introduction to Data Science', 'Data Mining', 'Data Warehouse'}
<class 'set'>
{'Introduction to Data Science', 'Data Mining', 'Data Warehouse'}

4 Dictionary (dict)

Unordered collection of key-value pairs.

course = {'name': 'Intro. to Data Science', 'code': 6101, 'credits': 3.00}
print(course)  # {'name': 'Intro. to Data Science', 'code': 6101, 'credits': 3.00}

print(type(course))  # <class 'dict'>

print(course['name'])  # Intro. to Data Science

course['name'] = 'Introduction to Data Science'
print(course['name'])  # Introduction to Data Science

course['prerequisite'] = True
print(course)  # {'name': 'Introduction to Data Science', 'code': 6101, 'credits': 3.00, 'prerequisite': True}

{'name': 'Intro. to Data Science', 'code': 6101, 'credits': 3.0}
<class 'dict'>
Intro. to Data Science
Introduction to Data Science
{'name': 'Introduction to Data Science', 'code': 6101, 'credits': 3.0, 'prerequisite': True}

Common Errors

Some frequent errors encountered when dealing with Data Structures in Python.

prerequisite_courses = ('Intro. to Data Science', 'Data Mining')
prerequisite_courses[0] = 'Introduction to Data Science'
print(prerequisite_courses)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[5], line 2
      1 prerequisite_courses = ('Intro. to Data Science', 'Data Mining')
----> 2 prerequisite_courses[0] = 'Introduction to Data Science'
      3 print(prerequisite_courses)

TypeError: 'tuple' object does not support item assignment

invalid_set = {['Intro. to Data Science', 'Data Mining']}

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[6], line 1
----> 1 invalid_set = {['Intro. to Data Science', 'Data Mining']}

TypeError: unhashable type: 'list'

course = {'name': 'Data Mining'}
print(course['credits'])

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
Cell In[7], line 2
      1 course = {'name': 'Data Mining'}
----> 2 print(course['credits'])

KeyError: 'credits'

prerequisite_courses = {'Intro. to Data Science', 'Data Mining'}
print(prerequisite_courses[0])

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[8], line 2
      1 prerequisite_courses = {'Intro. to Data Science', 'Data Mining'}
----> 2 print(prerequisite_courses[0])

TypeError: 'set' object is not subscriptable