List in Python (3)

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*Memo:

• My post explains a list (1).
• My post explains a list (2).
• My post explains a list (4).
• My post explains a list (5).
• My post explains a list (6).

A list can be enlarged with * and a number as shown below:

<1D list>:

v = [0, 1, 2, 3, 4] * 3

print(v)
# [0, 1, 2, 3, 4, 0, 1, 2, 3, 4, 0, 1, 2, 3, 4]

v = ['A', 'B', 'C', 'D', 'E'] * 3

print(v)
# ['A', 'B', 'C', 'D', 'E', 'A', 'B', 'C', 'D', 'E', 'A', 'B', 'C', 'D', 'E']

v = [] * 3

print(v)
# []

<2D list>:

v = [[0, 1, 2, 3, 4]] * 3

print(v)
# [[0, 1, 2, 3, 4], [0, 1, 2, 3, 4], [0, 1, 2, 3, 4]]

v = [['A', 'B', 'C', 'D', 'E']] * 3

print(v)
# [['A', 'B', 'C', 'D', 'E'],
#  ['A', 'B', 'C', 'D', 'E'],
#  ['A', 'B', 'C', 'D', 'E']]

v = [[]] * 3

print(v)
# [[], [], []]

<3D list>:

v = [[[0, 1, 2, 3, 4]]] * 3

print(v)
# [[[0, 1, 2, 3, 4]], [[0, 1, 2, 3, 4]], [[0, 1, 2, 3, 4]]]

v = [[['A', 'B', 'C', 'D', 'E']]] * 3

print(v)
# [[['A', 'B', 'C', 'D', 'E']],
#  [['A', 'B', 'C', 'D', 'E']],
#  [['A', 'B', 'C', 'D', 'E']]]

v = [[[]]] * 3

print(v)
# [[[]], [[]], [[]]]

A list and other lists can be concatenated with + as shown below:

v = [0, 1, 2] + [[3, 4]] + [[[5, 6, 7, 8]]]

print(v)
# [0, 1, 2, [3, 4], [[5, 6, 7, 8]]]

A list and other list cannot return:

• all the elements in them with '|' (Union: A ∪ B).
• their common elements with '&' (Intersection: A ∩ B).
• the elements in the list which aren't in other list with '-' (Difference: A - B).
• the elements in either the list or other list but not both with '^' (Symmetric Difference: A Δ B).

v = [0, 4] | [0, 2, 4]
# TypeError: unsupported operand type(s) for |: 'list' and 'list'

v = [0, 1, 2, 3] & [0, 2, 4]
# TypeError: unsupported operand type(s) for &: 'list' and 'list'

v = [0, 1, 2, 3] - [0, 2, 4]
# TypeError: unsupported operand type(s) for -: 'list' and 'list'

v = [0, 1, 2, 3] ^ [0, 2, 4]
# TypeError: unsupported operand type(s) for ^: 'list' and 'list'

A list can be iterated with a for statement as shown below:

<1D list>:

for x in [0, 1, 2, 3, 4]:
    print(x)
# 0
# 1
# 2
# 3
# 4

<2D list>:

for x in [[0, 1, 2, 3], [4, 5, 6, 7]]:
    for y in x:
        print(y)
# 0
# 1
# 2
# 3
# 4
# 5
# 6
# 7

<3D list>:

for x in [[[0, 1], [2, 3]], [[4, 5], [6, 7]]]:
    for y in x:
        for z in y:
            print(z)
# 0
# 1
# 2
# 3
# 4
# 5
# 6
# 7

A list can be unpacked with an assignment and for statement, function and * but not with ** as shown below:

v1, v2, v3 = [0, 1, 2]

print(v1, v2, v3)
# 0 1 2

v1, *v2, v3 = [0, 1, 2, 3, 4, 5]

print(v1, v2, v3)  # 0 [1, 2, 3, 4] 5
print(v1, *v2, v3) # 0 1 2 3 4 5

for v1, v2, v3 in [[0, 1, 2], [3, 4, 5]]:
    print(v1, v2, v3)
# 0 1 2
# 3 4 5

for v1, *v2, v3 in [[0, 1, 2, 3, 4, 5], [6, 7, 8, 9, 10, 11]]:
    print(v1, v2, v3)
    print(v1, *v2, v3)
# 0 [1, 2, 3, 4] 5
# 0 1 2 3 4 5
# 6 [7, 8, 9, 10] 11
# 6 7 8 9 10 11

print(*[0, 1], 2, *[3, 4, *[5]])
# 0 1 2 3 4 5

print([*[0, 1], 2, *[3, 4, *[5]]])
# [0, 1, 2, 3, 4, 5]

def func(p1='a', p2='b', p3='c', p4='d', p5='e', p6='f'):
    print(p1, p2, p3, p4, p5, p6)

func()
# a b c d e f

func(*[0, 1, 2, 3], *[4, 5])
# 0 1 2 3 4 5

def func(p1='a', p2='b', *args):
    print(p1, p2, args)
    print(p1, p2, *args)
    print(p1, p2, ['A', 'B', *args, 'C', 'D'])

func()
# a b ()
# a b Nothing
# a b ['A', 'B', 'C', 'D']

func(*[0, 1, 2, 3], *[4, 5])
# 0 1 (2, 3, 4, 5)
# 0 1 2 3 4 5
# 0 1 ['A', 'B', 2, 3, 4, 5, 'C', 'D']

list() can create a list with or without an iterable as shown below:

*Memo:

• The 1st argument is iterable(Optional-Default:()-Type:Iterable):
  • Don't use iterable=.

# Empty list
print(list())
print(list(()))
# []

print(list([0, 1, 2, 3, 4]))                      # list
print(list((0, 1, 2, 3, 4)))                      # tuple
print(list({0, 1, 2, 3, 4}))                      # set
print(list(frozenset([0, 1, 2, 3, 4])))           # frozenset
print(list(iter([0, 1, 2, 3, 4])))                # iterator
print(list(range(5)))                             # range
# [0, 1, 2, 3, 4]

print(list({'name': 'John', 'age': 36}))          # dict
print(list({'name': 'John', 'age': 36}.keys()))   # dict.keys()
# ['name', 'age']

print(list({'name': 'John', 'age': 36}.values())) # dict.values()
# ['John', 36]

print(list({'name': 'John', 'age': 36}.items()))  # dict.items()
# [('name', 'John'), ('age', 36)]

print(list('Hello'))                              # str
# ['H', 'e', 'l', 'l', 'o']

print(list(b'Hello'))                             # bytes
print(list(bytearray(b'Hello')))                  # bytearray
# [72, 101, 108, 108, 111]