6.3. Iterable Set

Important

• Only unique values

• Mutable - can add, remove, and modify items

• Stores only hashable elements (int, float, bool, None, str, tuple)

• Set is unordered data structure and do not record element position or insertion

• Do not support getitem and slice

• Contains in set has O(1) average case complexity [1]

✘

>>> users = {'alice', 'bob', 'carol', 'dave'}
>>> values = {1, 2, 3}

6.3.1. Define Empty

• data = set() - empty set

• No short syntax

✘

>>> data = set()

Problems:

✘

>>> data = {}  # dict

6.3.2. Define With Elements

• data = {1, 2, 3} - set with values

• Define With One Element

• Define With Many Elements

• Comma after last element of a one element set is optional

• Brackets are required

Define With One Element:

✘

>>> data = {1}
>>> data = {1,}

Define With Many Elements:

✘

>>> data = {1, 2, 3}
>>> data = {1.1, 2.2, 3.3}
>>> data = {True, False, None}
>>> data = {'a', 'b', 'c'}
>>> data = {'a', 1, 2.2, True, None}

Comma after last element of a one element set is optional. Brackets are required

6.3.3. Unique Values

• Sets store only unique values

• Compares by values, not types

✘

>>> data = {1, 2, 3, 1}
>>>
>>> data
{1, 2, 3}

Compares by values, not types:

✘

>>> data = {1, 1.0}
>>> data
{1}

✘

>>> data = {1.0, 1}
>>> data
{1.0}

6.3.4. Hashable

• Can store elements of any hashable types

• Hashable: int, float, bool, None, str, tuple

• Non-hashable: list, set, dict

✘

>>> data = set()
>>>
>>> data.add(1)
>>> data.add(2.2)
>>> data.add(True)
>>> data.add(None)
>>> data.add('a')
>>> data.add((1, 2, 3))
>>>
>>> data.add([1, 2, 3])
Traceback (most recent call last):
TypeError: unhashable type: 'list'
>>>
>>> data.add({1, 2, 3})
Traceback (most recent call last):
TypeError: unhashable type: 'set'

Hashable (Immutable):

• int

• float

• bool

• NoneType

• str

• tuple

Non-hashable (Mutable):

• list

• set

• dict

"Hashable types are also immutable" is true for builtin types, but it's not a universal truth. More information in OOP Hash.

✘

>>> hash(1.1)
230584300921369601

✘

>>> hash('a')
7717683026012469353

✘

>>> hash((1,2,3))
529344067295497451

✘

>>> hash([1,2,3])
Traceback (most recent call last):
TypeError: unhashable type: 'list'

✘

>>> hash({1,2,3})
Traceback (most recent call last):
TypeError: unhashable type: 'set'

6.3.5. Conversion

• set() converts argument to set

✘

>>> data = [1, 2, 3]
>>> set(data)
{1, 2, 3}

✘

>>> data = (1, 2, 3)
>>> set(data)
{1, 2, 3}

6.3.6. Deduplicate

• Converting to set will deduplicate items

• Works with str, list, tuple

Converting to set will deduplicate items:

✘

>>> data = [1, 2, 3, 1]
>>> set(data)
{1, 2, 3}

6.3.7. Add

• set.add() - method

• Adds element to set

• Adds only unique values

• Adds only hashable values

Adds element to set:

✘

>>> data = {1, 2, 3}
>>> data.add(4)
>>>
>>> data
{1, 2, 3, 4}

Adds only unique values:

✘

>>> data = {1, 2, 3}
>>> data.add(3)
>>>
>>> data
{1, 2, 3}

6.3.8. Update

• set.update() - method

• Adds all elements from the sequence to the set

• Adds only unique values

• Adds only hashable values

✘

>>> data = {1, 2, 3}
>>>
>>> data.update({3, 4, 5})
>>> data
{1, 2, 3, 4, 5}

6.3.9. Pop

Gets and remove items

✘

>>> data = {1, 2, 3}
>>> data.pop()
1
>>>
>>> data
{2, 3}

6.3.10. Membership

• in - check if element is in set

✘

>>> data = {1, 2, 3}
>>>
>>> 1 in data
True
>>> 0 in data
False

6.3.11. Union

• Returns sum of elements from both sets

• set.union() - method

• | - operator

✘

>>> a = {1, 2, 3}
>>> b = {3, 4, 5}
>>>
>>> a.union(b)
{1, 2, 3, 4, 5}
>>>
>>> a | b
{1, 2, 3, 4, 5}

6.3.12. Union Update

• Adds to a all elements of b

✘

>>> a = {1, 2, 3}
>>> b = {3, 4, 5}
>>>
>>> a |= b
>>> a
{1, 2, 3, 4, 5}

6.3.13. Is Disjoint

• Check if sets have common elements

• Returns True or False

• True - if sets don't have common elements

• False - if sets have common elements

• set.isdisjoint() - method

✘

>>> a = {1, 2, 3}
>>> b = {3, 4, 5}
>>>
>>> a.isdisjoint(b)
False

6.3.14. Is Subset

• Check if b has all elements from a

• Returns True or False

• True - if b has all elements from a

• False - if b don't have element from a

• set.issubset() - method

• < - proper subset

• <= - subset

✘

>>> a = {1, 2, 3}
>>> b = {3, 4, 5}
>>>
>>> a.issubset(b)
False
>>>
>>> a < b
False
>>>
>>> a <= b
False

6.3.15. Is Superset

• Check if a has all elements from b

• True - if a has all elements from b

• False - if a don't have element from b

• set.issuperset() - method

• > - proper superset

• >= - superset

✘

>>> a = {1, 2, 3}
>>> b = {3, 4, 5}
>>>
>>> a.issuperset(b)
False
>>>
>>> a > b
False
>>>
>>> a >= b
False

6.3.16. Difference

• Returns elements from a which are not in b

• set.difference() - method

• - - operator

✘

>>> a = {1, 2, 3}
>>> b = {3, 4, 5}
>>>
>>> a.difference(b)
{1, 2}
>>>
>>> a - b
{1, 2}

6.3.17. Symmetric Difference

• Returns elements from a and b, but without common elements

• set.symmetric_difference() - method

• ^ - operator

✘

>>> a = {1, 2, 3}
>>> b = {3, 4, 5}
>>>
>>> a.symmetric_difference(b)
{1, 2, 4, 5}
>>>
>>> a ^ b
{1, 2, 4, 5}

6.3.18. Intersection

• Returns common element from in a and b

• set.intersection() - method

• & - operator

✘

>>> a = {1, 2, 3}
>>> b = {3, 4, 5}
>>>
>>> a.intersection(b)
{3}
>>>
>>> a & b
{3}

6.3.19. Cardinality

• Number of elements in set

• len() - function

✘

>>> data = {1, 2, 3}
>>> len(data)
3

6.3.20. References

[1]

https://wiki.python.org/moin/TimeComplexity

6.3.21. Assignments

# %% About
# - Name: Iterable Set Definition
# - Difficulty: easy
# - Lines: 5
# - Minutes: 3

# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author

# %% English
# 1. Define `result_a` as a `set` without elements
# 2. Define `result_b` as a `set` with elements: 1, 2, 3
# 3. Define `result_c` as a `set` with elements: 1.1, 2.2, 3.3
# 4. Define `result_d` as a `set` with elements: 'a', 'b', 'c'
# 5. Define `result_e` as a `set` with elements: True, False, None
# 6. Define `result_f` as a `set` with elements: 1, 2.2, True, 'a'
# 7. Run doctests - all must succeed

# %% Polish
# 1. Zdefiniuj `result_a` jako `set` bez elementów
# 2. Zdefiniuj `result_b` jako `set` z elementami: 1, 2, 3
# 3. Zdefiniuj `result_c` jako `set` z elementami: 1.1, 2.2, 3.3
# 4. Zdefiniuj `result_d` jako `set` z elementami: 'a', 'b', 'c'
# 5. Zdefiniuj `result_e` jako `set` z elementami: True, False, None
# 6. Zdefiniuj `result_f` jako `set` z elementami: 1, 2.2, True, 'a'
# 7. Uruchom doctesty - wszystkie muszą się powieść

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'

>>> assert result_a is not Ellipsis, \
'Assign your result to variable `result_a`'
>>> assert result_b is not Ellipsis, \
'Assign your result to variable `result_b`'
>>> assert result_c is not Ellipsis, \
'Assign your result to variable `result_c`'
>>> assert result_d is not Ellipsis, \
'Assign your result to variable `result_d`'
>>> assert result_e is not Ellipsis, \
'Assign your result to variable `result_e`'
>>> assert result_f is not Ellipsis, \
'Assign your result to variable `result_f`'

>>> assert type(result_a) is set, \
'Variable `result_a` has invalid type, should be set'
>>> assert type(result_b) is set, \
'Variable `result_b` has invalid type, should be set'
>>> assert type(result_c) is set, \
'Variable `result_c` has invalid type, should be set'
>>> assert type(result_d) is set, \
'Variable `result_d` has invalid type, should be set'
>>> assert type(result_e) is set, \
'Variable `result_e` has invalid type, should be set'
>>> assert type(result_f) is set, \
'Variable `result_f` has invalid type, should be set'

>>> assert result_a == set(), \
'Variable `result_a` has invalid value, should be set()'
>>> assert result_b == {1, 2, 3}, \
'Variable `result_b` has invalid value, should be {1, 2, 3}'
>>> assert result_c == {1.1, 2.2, 3.3}, \
'Variable `result_c` has invalid value, should be {1.1, 2.2, 3.3}'
>>> assert result_d == {'a', 'b', 'c'}, \
'Variable `result_d` has invalid value, should be {"a", "b", "c"}'
>>> assert result_e == {True, False, None}, \
'Variable `result_e` has invalid value, should be {True, False, None}'
>>> assert result_f == {1, 2.2, True, 'a'}, \
'Variable `result_f` has invalid value, should be {1, 2.2, True, "a"}'
"""

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% Imports

# %% Types
result_a: set
result_b: set[int]
result_c: set[float]
result_d: set[str]
result_e: set[bool|None]
result_f: set[int|float|bool|str]

# %% Data

# %% Result
result_a = ...
result_b = ...
result_c = ...
result_d = ...
result_e = ...
result_f = ...

# %% About
# - Name: Type Set Add
# - Difficulty: easy
# - Lines: 1
# - Minutes: 2

# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author

# %% English
# 1. Insert 'black' to the `result`
# 2. Run doctests - all must succeed

# %% Polish
# 1. Wstaw 'black' do `result`
# 2. Uruchom doctesty - wszystkie muszą się powieść

# %% Hints
# - `set.add()`

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'

>>> assert result is not Ellipsis, \
'Assign your result to variable `result`'

>>> assert type(result) is set, \
'Variable `result` has invalid type, should be set'

>>> sorted(result)
['black', 'blue', 'green', 'red']
"""

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% Imports

# %% Types
result: set[str]

# %% Data
result = {'red', 'green', 'blue'}

# %% Result

# %% About
# - Name: Type Set Update
# - Difficulty: easy
# - Lines: 1
# - Minutes: 2

# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author

# %% English
# 1. Insert all elements from `data` to the `result`
# 2. Run doctests - all must succeed

# %% Polish
# 1. Wstaw wszystkie elementy z `data` do `result`
# 2. Uruchom doctesty - wszystkie muszą się powieść

# %% Hints
# - `set.update()`

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'

>>> assert result is not Ellipsis, \
'Assign your result to variable `result`'

>>> assert type(result) is set, \
'Variable `result` has invalid type, should be set'

>>> sorted(result)
['black', 'blue', 'green', 'red', 'white']
"""

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% Imports

# %% Types
result: set[str]

# %% Data
DATA = {'black', 'white'}
result = {'red', 'green', 'blue'}

# %% Result

# %% About
# - Name: Iterable Set Len
# - Difficulty: easy
# - Lines: 1
# - Minutes: 2

# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author

# %% English
# 1. Define `result` with a result of checking length of `DATA`
# 2. Run doctests - all must succeed

# %% Polish
# 1. Zdefiniuj `result` z wynikiem sprawdzenia długości `DATA`
# 2. Uruchom doctesty - wszystkie muszą się powieść

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'

>>> assert result is not Ellipsis, \
'Assign your result to variable `result`'

>>> assert type(result) is int, \
'Variable `result` has invalid type, should be int'

>>> result
3
"""

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% Imports

# %% Types
result: int

# %% Data
DATA = {'red', 'green', 'blue'}

# %% Result
result = ...

# %% About
# - Name: Iterable Set Contains
# - Difficulty: easy
# - Lines: 1
# - Minutes: 2

# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author

# %% English
# 1. Define `result` with a result of checking if 'black' is in the `DATA`
# 2. Run doctests - all must succeed

# %% Polish
# 1. Zdefiniuj `result` z wynikiem sprawdzenia czy 'black' jest w `DATA`
# 2. Uruchom doctesty - wszystkie muszą się powieść

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0
>>> assert sys.version_info >= (3, 9), \
'Python 3.9+ required'

>>> assert result is not Ellipsis, \
'Assign your result to variable `result`'

>>> assert type(result) is bool, \
'Variable `result` has invalid type, should be bool'

>>> result
False
"""

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -v myfile.py`

# %% Imports

# %% Types
result: bool

# %% Data
DATA = {'red', 'green', 'blue'}

# %% Result
result = ...