List in Python (2)

Buy Me a Coffee☕

*Memo:

• My post explains a list and the list with indexing.
• My post explains list functions (1).
• My post explains list functions (2).

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]

A list comprehension can create a list as shown below:

<1D list>:

sample = [0, 1, 2, 3, 4, 5, 6, 7]

v = [x**2 for x in sample]

print(v)
# [0, 1, 4, 9, 16, 25, 36, 49]

<2D list>:

sample = [[0, 1, 2, 3], [4, 5, 6, 7]]

v = [[y**2 for y in x] for x in sample]

print(v)
# [[0, 1, 4, 9], [16, 25, 36, 49]]

<3D list>:

sample = [[[0, 1], [2, 3]], [[4, 5], [6, 7]]]

v = [[[z**2 for z in y] for y in x] for x in sample]

print(v)
# [[[0, 1], [4, 9]], [[16, 25], [36, 49]]]

A list can be read or changed by indexing as shown below:

*Memo:

• Indexing can be done with one or more [index].
• A del statement can remove one or more elements from a list by indexing and can remove one or more variables themselves.

<1D list>:

v = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']

print(v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7])
print(v[-8], v[-7], v[-6], v[-5], v[-4], v[-3], v[-2], v[-1])
# a b c d e f g h

v[1] = 'B'
v[-7] = 'B'

v[3] = 'D'
v[-5] = 'D'

v[6] = 'G'
v[-2] = 'G'

print(v)
# ['a', 'B', 'c', 'D', 'e', 'f', 'G', 'h']

del v[1], v[2], v[4]
# del v[-7], v[-5], v[-2]

print(v)
# ['a', 'c', 'e', 'f', 'h']

del v

print(v)
# NameError: name 'v' is not defined

<2D list>:

v = [['a', 'b', 'c', 'd'], ['e', 'f', 'g', 'h']]

print(v[0], v[1])
print(v[-2], v[-1])
# ['a', 'b', 'c', 'd'] ['e', 'f', 'g', 'h']

print(v[0][0], v[0][1], v[0][2], v[0][3], v[1][0], v[1][1], v[1][2], v[1][3])
print(v[-2][-4], v[-2][-3], v[-2][-2], v[-2][-1],
      v[-1][-4], v[-1][-3], v[-1][-2], v[-1][-1])
# a b c d e f g h

v[0][1] = 'B'
v[-2][-3] = 'B'

v[1] = ['E', 'F', 'G', 'H']
v[-1] = ['E', 'F', 'G', 'H']

print(v)
# [['a', 'B', 'c', 'd'], ['E', 'F', 'G', 'H']]

del v[0][1], v[1]
# del v[-2][-3], v[-1]

print(v)
# [['a', 'c', 'd']]

<3D list>:

v = [[['a', 'b'], ['c', 'd']], [['e', 'f'], ['g', 'h']]]

print(v[0], v[1])
print(v[-2], v[-1])
# [['a', 'b'], ['c', 'd']] [['e', 'f'], ['g', 'h']]

print(v[0][0], v[0][1], v[1][0], v[1][1])
print(v[-2][-2], v[-2][-1], v[-1][-2], v[-1][-1])
# ['a', 'b'] ['c', 'd'] ['e', 'f'] ['g', 'h']

print(v[0][0][0], v[0][0][1], v[0][1][0], v[0][1][1], v[1][0][0],
      v[1][0][1], v[1][1][0], v[1][1][1])
print(v[-2][-2][-2], v[-2][-2][-1], v[-2][-1][-2], v[-2][-1][-1],
      v[-1][-2][-2], v[-1][-2][-1], v[-1][-1][-2], v[-1][-1][-1])
# a b c d e f g h

v[0][0][1] = 'B'
v[-2][-2][-1] = 'B'

v[0][1] = 'C'
v[-2][-1] = 'C'

v[1] = ['D', ['E', 'F']]
v[-1] = ['D', ['E', 'F']]

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

del v[0][0][1], v[0][1], v[1]
# del v[-2][-2][-1], v[-2][-1], v[-1]

print(v)
# [[['a']]]