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Super Kai (Kazuya Ito)
Super Kai (Kazuya Ito)

Posted on • Edited on

List in Python (3)

#python #list #brackets #function

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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'], []]
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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'], []]
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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']
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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']
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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) # []
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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']
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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
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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
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