List in Python (3)

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*Memo:

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

append() can add a value to the end of the list as shown below:

*Memo:

• The 1st argument is object(Required-Type:Any):
  • An object is added as it is.
  • Don't use object=.

v = ['A', 'B']

v.append('C')
print(v)
# ['A', 'B', 'C']

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

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

extend() can add an iterable to the end of the list as shown below:

*Memo:

• The 1st argument is iterable(Required-Iterable):
  • The iterable unpacked is added.
  • Don't use iterable=.

v = ['A', 'B']

v.extend('C')
print(v)
# ['A', 'B', 'C']

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

v.extend([['F', 'G']])
print(v)
# ['A', 'B', 'C', 'D', 'E', ['F', 'G']]

v.extend([])
print(v)
# ['A', 'B', 'C', 'D', 'E', ['F', 'G']]

v.extend([[]])
print(v)
# ['A', 'B', 'C', 'D', 'E', ['F', 'G'], []]

insert() can add a value to the selected index in the list as shown below:

*Memo:

• The 1st argument is index(Required-Type:int):
  • Don't use index=.
• The 2nd argument is object(Required-Type:Any):
  • Don't use object=.

v = ['a', 'b']

v.insert(1, 'X')
print(v)
# ['a', 'X', 'b']

v.insert(0, ['Y', 'Z'])
print(v)
# [['Y', 'Z'], 'a', 'X', 'b']

v.insert(3, [])
print(v)
# [['Y', 'Z'], 'a', 'X', [], 'b']

remove() can remove the 1st element matched to value from the list, searching from the left to the right in the list as shown below:

*Memo:

• The 1st argument is value(Required-Type:Any):
  • Don't use value=.
• Error occurs if value doesn't exist.

v = ['A', 'B', 'C', 'D', 'E', ['F', 'G', 'H'], ['I', 'J']]

v.remove('C')
print(v)
# ['A', 'B', 'D', 'E', ['F', 'G', 'H'], ['I', 'J']]

# v.remove('F')
# v.remove(['F'])
# v.remove(['F', 'G']) 
# ValueError: list.remove(x): x not in list

v.remove(['F', 'G', 'H'])
print(v)
# ['A', 'B', 'D', 'E', ['I', 'J']]

v[4].remove('I')
print(v)
# ['A', 'B', 'D', 'E', ['J']]

v[4].remove('J')
print(v)
# ['A', 'B', 'D', 'E', []]

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

clear() can remove all elements from the list as shown below:

*Memo:

• It has no arguments:

v = ['A', 'B', 'C', 'D', 'E', ['F', 'G', 'H'], ['I', 'J']]

v[5].clear()
print(v)
# ['A', 'B', 'C', 'D', 'E', [], ['I', 'J']]

v[6].clear()
print(v)
# ['A', 'B', 'C', 'D', 'E', [], []]

v.clear()
print(v)
# []

pop() can remove and throw the element selected by index from the list as shown below:

*Memo:

• The 1st argument is index(Required-Default:-1-Type:int):
  • -1 means the last index.
  • Don't use index=.

v = ['A', 'B', 'C', 'D', 'E', ['F', 'G', 'H'], ['I', 'J']]

print(v.pop(2)) # C
print(v)        # ['A', 'B', 'D', 'E', ['F', 'G', 'H'], ['I', 'J']]

print(v.pop(4)) # ['F', 'G', 'H']
print(v)        # ['A', 'B', 'D', 'E', ['I', 'J']]

print(v[4].pop(0)) # I
print(v)           # ['A', 'B', 'D', 'E', ['J']]

print(v[4].pop(0)) # J
print(v)           # ['A', 'B', 'D', 'E', []]

print(v.pop(4)) # []
print(v)        # ['A', 'B', 'D', 'E']

index() can get the 1st index of the element matched to value from the list between [start, end), searching from the left to the right in the list as shown below:

*Memo:

• The 1st argument is value(Required-Type:Any).
• The 2nd argument is start(Optional-Default:0-Type:int):
  • It's a start index(inclusive).
  • Don't use start=.
• The 3rd argument is end(Optional-Default:9223372036854775807-Type:int):
  • It's an end index(exclusive).
  • Don't use end=.
• Error occurs if value doesn't exist.

v = ['A', 'B', 'C', 'D', 'A', 'B', 'C', 'D']

print(v.index('B'))                         # 1
print(v.index('B', 0, 9223372036854775807)) # 1
print(v.index('B', 2))                      # 5
print(v.index('B', 2, 6))                   # 5
print(v.index('B', 2, 5))                   # ValueError: 'B' is not in list

count() can count the elements matched to value in the list as shown below:

*Memo:

• The 1st argument is value(Required-Type:Any):
  • Don't use value=.

v = ['A', 'B', 'C', 'A', 'B', 'B', 'A', 'B']

print(v.count('A')) # 3
print(v.count('B')) # 4
print(v.count('C')) # 1
print(v.count('a')) # 0
print(v.count('D')) # 0