List in Python (4)

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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 (1).

sort() can sort the list as shown below:

*Memo:

• The 1st argument is key(Optional-Default:None-Type:Callable or NoneType).
• The 2nd argument is reverse(Optional-Default:False-Type:bool) to reverse the list.
• sort() doesn't create a copy different from sorted().

v = [3, 5, -2, 1, -4]

v.sort()
v.sort(key=None, reverse=False)
print(v)
# [-4, -2, 1, 3, 5]

v.sort(reverse=True)
print(v)
# [5, 3, 1, -2, -4]

v.sort(key=abs)
print(v)
# [1, -2, 3, -4, 5]

v.sort(key=abs, reverse=True)
print(v)
# [5, -4, 3, -2, 1]

v = ["apple", "Banana", "Kiwi", "cherry"]

# Case sensitive sort
v.sort()
print(v)
# ['Banana', 'Kiwi', 'apple', 'cherry']

# Case insensitive sort
v.sort(key=str.upper)
v.sort(key=str.lower)
print(v)
# ['apple', 'Banana', 'cherry', 'Kiwi']

# Sort by the length of a word
v.sort(key=len)
print(v)
# ['Kiwi', 'apple', 'Banana', 'cherry']

sorted() can sort a list as shown below:

*Memo:

• The 1st argument is iterable(Required-Type:Iterable):
  • Don't use iterable=.
• The 2nd argument is key(Optional-Default:None-Type:Callable or NoneType)).
• The 3rd argument is reverse(Optional-Default:False-Type:bool) to reverse the list.
• sorted() creates a copy different from sort():
  • Be careful, sorted() does shallow copy instead of deep copy as my issue.

v = [3, 5, -2, 1, -4]

print(sorted(v))
print(sorted(v, key=None, reverse=False))
# [-4, -2, 1, 3, 5]

print(sorted(v, reverse=True))
# [5, 3, 1, -2, -4]

print(sorted(v, key=abs))
# [1, -2, 3, -4, 5]

print(sorted(v, key=abs, reverse=True))
# [5, -4, 3, -2, 1]

v = ["apple", "Banana", "Kiwi", "cherry"]

# Case sensitive sort
print(sorted(v))
# ['Banana', 'Kiwi', 'apple', 'cherry']

# Case insensitive sort
print(sorted(v, key=str.upper))
print(sorted(v, key=str.lower))
# ['apple', 'Banana', 'cherry', 'Kiwi']

# Sort by the length of a word
print(sorted(v, key=len))
# ['Kiwi', 'apple', 'Banana', 'cherry']

reverse() can reverse the list as shown below:

*Memo:

• It has no arguments.

v = [3, 5, -2, 1, -4]

v.reverse()
print(v)
# [-4, 1, -2, 5, 3]

v = ["apple", "Banana", "Kiwi", "cherry"]

v.reverse()
print(v)
# ['cherry', 'Kiwi', 'Banana', 'apple']

reversed() can return the iterator which has the reversed elements of a list, then the iterator is converted to a list with list() as shown below:

*Memo:

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

v = [3, 5, -2, 1, -4]

print(reversed(v))
# <list_reverseiterator object at 0x000001F3B993B280>

print(list(reversed(v)))
# [-4, 1, -2, 5, 3]

v = ["apple", "Banana", "Kiwi", "cherry"]

print(list(reversed(v)))
# ['cherry', 'Kiwi', 'Banana', 'apple']