4.5. Sequence Nested

  • Sequence is an object

  • Sequence element is an object too

  • Therefore an element of a sequence could be another sequence

  • There is no limit how nested it could be

>>> int.mro()
[<class 'int'>, <class 'object'>]
>>>
>>> float.mro()
[<class 'float'>, <class 'object'>]
>>>
>>> bool.mro()
[<class 'bool'>, <class 'int'>, <class 'object'>]
>>>
>>> type(None).mro()
[<class 'NoneType'>, <class 'object'>]
>>>
>>> tuple.mro()
[<class 'tuple'>, <class 'object'>]
>>>
>>> list.mro()
[<class 'list'>, <class 'object'>]
>>>
>>> set.mro()
[<class 'set'>, <class 'object'>]

>>> obj = 1
>>> data = [obj, obj, obj]
>>> data
[1, 1, 1]

>>> obj = [1, 2, 3]
>>> data = [obj, obj, obj]
>>> data  
[[1, 2, 3],
 [1, 2, 3],
 [1, 2, 3]]

4.5.1. List of Lists

Also known as multidimensional lists or matrix.

Readability differs depending on whitespaces:

>>> a = [[1,2,3],[4,5,6],[7,8,9]]

>>> b = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

>>> c = [[1,2,3], [4,5,6], [7,8,9]]

>>> d = [
...      [1, 2, 3],
...      [4, 5, 6],
...      [7, 8, 9],
... ]

>>> e = [
...      [1, 2, 3],
...      [4, 5, 6],
...      [7, 8, 9]]

>>> f = [[1, 2, 3],
...      [4, 5, 6],
...      [7, 8, 9],
... ]

>>> g = [[1, 2, 3],
...      [4, 5, 6],
...      [7, 8, 9]]

Length:

>>> data = [[1, 2, 3],
...         [4, 5, 6],
...         [7, 8, 9]]
>>>
>>> len(data)
3
>>> len(data[0])
3

4.5.2. List of Tuples

Readability differs depending on whitespaces:

>>> data = [(4.7, 3.2, 1.3, 0.2, 'setosa'),
...         (7.0, 3.2, 4.7, 1.4, 'versicolor'),
...         (7.6, 3.0, 6.6, 2.1, 'virginica')]

>>> data = [
...     (4.7, 3.2, 1.3, 0.2, 'setosa'),
...     (7.0, 3.2, 4.7, 1.4, 'versicolor'),
...     (7.6, 3.0, 6.6, 2.1, 'virginica')]

>>> data = [
...     (4.7, 3.2, 1.3, 0.2, 'setosa'),
...     (7.0, 3.2, 4.7, 1.4, 'versicolor'),
...     (7.6, 3.0, 6.6, 2.1, 'virginica'),
... ]

Append elements using list.append():

>>> data = [
...     (4.7, 3.2, 1.3, 0.2, 'setosa'),
...     (7.0, 3.2, 4.7, 1.4, 'versicolor'),
...     (7.6, 3.0, 6.6, 2.1, 'virginica')]
>>>
>>> row = (4.9, 2.5, 4.5, 1.7, 'virginica')
>>>
>>> data.append(row)
>>> data  
[(4.7, 3.2, 1.3, 0.2, 'setosa'),
 (7.0, 3.2, 4.7, 1.4, 'versicolor'),
 (7.6, 3.0, 6.6, 2.1, 'virginica'),
 (4.9, 2.5, 4.5, 1.7, 'virginica')]

Append elements using list.extend():

>>> data = [
...     (4.7, 3.2, 1.3, 0.2, 'setosa'),
...     (7.0, 3.2, 4.7, 1.4, 'versicolor'),
...     (7.6, 3.0, 6.6, 2.1, 'virginica')]
>>>
>>> row = (4.9, 2.5, 4.5, 1.7, 'virginica')
>>>
>>> data.extend(row)
>>> data  
[(4.7, 3.2, 1.3, 0.2, 'setosa'),
 (7.0, 3.2, 4.7, 1.4, 'versicolor'),
 (7.6, 3.0, 6.6, 2.1, 'virginica'),
 4.9,
 2.5,
 4.5,
 1.7,
 'virginica']

Length:

>>> data = [
...     (4.7, 3.2, 1.3, 0.2, 'setosa'),
...     (7.0, 3.2, 4.7, 1.4, 'versicolor'),
...     (7.6, 3.0, 6.6, 2.1, 'virginica')]
>>>
>>> len(data)
3
>>> len(data[0])
5

4.5.3. Many Types

Readability differs depending on whitespaces:

>>> data = [
...     [1, 2],
...     (3, 4, 5, 6),
...     {7, 8, 9, 10, 11}]
>>>
>>> data = [
...     [1, 2],
...     (3, 4, 5, 6),
...     {7, 8, 9, 10, 11}
... ]
>>>
>>> data = [[1, 2],
...         (3, 4, 5, 6),
...         {7, 8, 9, 10, 11}]

Length:

>>> data = [[1, 2],
...         (3, 4, 5, 6),
...         {7, 8, 9, 10, 11}]
>>>
>>> len(data)
3
>>> len(data[0])
2
>>> len(data[1])
4
>>> len(data[2])
5

4.5.4. Use Case - 0x01

One dimensional (1D) structure - vector:

>>> from pprint import pprint
>>>
>>>
>>> obj1 = 1
>>> obj2 = 2
>>> obj3 = 3
>>> data = [obj1, obj2, obj3]
>>>
>>> pprint(data, width=20)
[1, 2, 3]

Two dimensional (2D) structure - matrix:

>>> from pprint import pprint
>>>
>>>
>>> obj1 = [1, 2, 3]
>>> obj2 = [4, 5, 6]
>>> obj3 = [7, 8, 9]
>>> data = [obj1, obj2, obj3]
>>>
>>> pprint(data, width=20)
[[1, 2, 3],
 [4, 5, 6],
 [7, 8, 9]]

Three dimensional (3D) structure - tensor:

>>> from pprint import pprint
>>>
>>>
>>> obj1 = [[1,2,3], [4,5,6], [7,8,9]]
>>> obj2 = [[10,20,30], [40,50,60], [70,80,90]]
>>> obj3 = [[100,200,300], [400,500,600], [700,800,900]]
>>> data = [obj1, obj2, obj3]
>>>
>>> pprint(data, width=20)
[[[1, 2, 3],
  [4, 5, 6],
  [7, 8, 9]],
 [[10, 20, 30],
  [40, 50, 60],
  [70, 80, 90]],
 [[100, 200, 300],
  [400, 500, 600],
  [700, 800, 900]]]

4.5.5. Assignments

Code 4.9. Solution
"""
* Assignment: Sequence Nested Create
* Required: yes
* Complexity: easy
* Lines of code: 4 lines
* Time: 3 min

English:
    1. Create nested list `result` with elements:
        a. tuple: 1, 2, 3
        b. list: 1.1, 2.2, 3.3
        c. set: 'red', 'green', 'blue'
    2. Run doctests - all must succeed

Polish:
    1. Stwórz zagnieżdżoną listę `result` z elementami:
        a. tuple: 1, 2, 3
        b. list: 1.1, 2.2, 3.3
        c. set: 'red', 'green', 'blue'
    2. Uruchom doctesty - wszystkie muszą się powieść

Tests:
    >>> import sys; sys.tracebacklimit = 0

    >>> assert result is not Ellipsis, \
    'Assign your result to variable `result`'
    >>> assert type(result) is list, \
    'Variable `result` has invalid type, should be list'
    >>> assert len(result) == 3, \
    'Variable `result` length should be 3'

    >>> assert (1, 2, 3) in result
    >>> assert [1.1, 2.2, 3.3] in result
    >>> assert {'red', 'green', 'blue'} in result
"""

# With tuple 1, 2, 3 and list 1.1, 2.2, 3.3
# And set 'red', 'green', 'blue'
# type: list[tuple|list|set]
result = ...