DEV Community

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

Posted on • Edited on

Set in Python (3)

#python #set #curlybraces #function

Buy Me a Coffee☕

*Memo:

  • My post explains a set and the set with copy.
  • My post explains set functions (1).

difference() can return the zero or more elements which the set has but *others don't have as shown below:

*Memos:

  • The 1st arguments are *others(Optional-Default:()-Type:Iterable):
    • Don't use any keywords like *others=, others=, etc.
  • - also does difference() but - doesn't support the combination of a set and list or tuple.
  • difference() creates a copy while difference_update() doesn't. 
A = {10, 20, 30, 40} B = {10, 30, 50} C = {30, 40} print(A.difference(B)) # {40, 20} print(A.difference(C)) # {10, 20} print(A.difference(B, C)) # {20} print(A.difference()) # {40, 10, 20, 30}  print(A - B) # {40, 20} print(A - C) # {10, 20} print(A - B - C) # {20} print(A) # {40, 10, 20, 30}
Enter fullscreen mode Exit fullscreen mode 
A = {10, 20, 30, 40} # set B = [10, 30, 50] # list C = (30, 40) # tuple  print(A.difference(B)) # {40, 20} print(A.difference(C)) # {10, 20} print(A.difference(B, C)) # {20} print(A.difference()) # {40, 10, 20, 30}
Enter fullscreen mode Exit fullscreen mode

difference_update() can return the zero or more elements which the set has but *others don't have as shown below:

*Memo:

  • The 1st arguments are *others(Optional-Default:()-Type:Iterable):
    • Don't use any keywords like *others=, others=, etc.
  • -= with or without | also does difference_update() but -= and | don't support the combination of a set and list or tuple.
  • difference_update() doesn't create a copy while difference() does. 
A = {10, 20, 30, 40} B = {10, 30, 50} C = {30, 40} A.difference_update(B) print(A) # {20, 40}  A.difference_update(C) print(A) # {20}  A.difference_update(B, C) print(A) # {20}  A.difference_update() print(A) # {20}
Enter fullscreen mode Exit fullscreen mode 
A = {10, 20, 30, 40} # set B = [10, 30, 50] # list C = (30, 40) # tuple  A.difference_update(B) print(A) # {20, 40}  A.difference_update(C) print(A) # {20}  A.difference_update(B, C) print(A) # {20}  A.difference_update() print(A) # {20}
Enter fullscreen mode Exit fullscreen mode 
A = {10, 20, 30, 40} B = {10, 30, 50} C = {30, 40} A -= B print(A) # {20, 40}  A -= C print(A) # {40}  A -= B | C print(A) # {40}
Enter fullscreen mode Exit fullscreen mode

symmetric_difference() can return the zero or more elements which the set has but other doesn't have or which the set doesn't have but other has as shown below:

*Memo:

  • The 1st argument is other(Required-Type:Iterable):
    • Don't use other=.
  • ^ also does symmetric_difference() but ^ doesn't support the combination of a set and list or tuple.
  • symmetric_difference() creates a copy while symmetric_difference_update() doesn't. 
A = {10, 20, 30, 40} B = {10, 30, 50} C = {30, 40} print(A.symmetric_difference(B)) # {40, 50, 20} print(A.symmetric_difference(C)) # {10, 20}  print(A ^ B) # {40, 50, 20} print(A ^ C) # {10, 20}
Enter fullscreen mode Exit fullscreen mode 
A = {10, 20, 30, 40} # set B = [10, 30, 50] # list C = (30, 40) # tuple  print(A.symmetric_difference(B)) # {40, 50, 20} print(A.symmetric_difference(C)) # {10, 20}
Enter fullscreen mode Exit fullscreen mode

symmetric_difference_update() can return the zero or more elements which the set has but other doesn't have or which the set doesn't have but other has as shown below:

*Memo:

  • The 1st argument is other(Required-Type:Iterable):
    • Don't use other=.
  • ^= also does symmetric_difference_update() but ^= doesn't support the combination of a set and list or tuple.
  • symmetric_difference_update() doesn't create a copy while symmetric_difference() does. 
A = {10, 20, 30, 40} B = {10, 30, 50} C = {30, 40} A.symmetric_difference_update(B) print(A) # {40, 50, 20}  A.symmetric_difference_update(C) print(A) # {50, 20, 30}
Enter fullscreen mode Exit fullscreen mode 
A = {10, 20, 30, 40} # set B = [10, 30, 50] # list C = (30, 40) # tuple  A.symmetric_difference_update(B) print(A) # {40, 50, 20}  A.symmetric_difference_update(C) print(A) # {50, 20, 30}
Enter fullscreen mode Exit fullscreen mode 
A = {10, 20, 30, 40} B = {10, 30, 50} C = {30, 40} A ^= B print(A) # {40, 50, 20}  A ^= C print(A) # {50, 20, 30}
Enter fullscreen mode Exit fullscreen mode

isdisjoint() can check if the set and other don't have any common elements as shown below:

*Memo:

  • The 1st argument is other(Required-Type:Iterable):
    • Don't use other=. 
A = {10, 20, 30} B = {40, 50} C = {30, 40} print(A.isdisjoint(B)) # True print(A.isdisjoint(C)) # False
Enter fullscreen mode Exit fullscreen mode 
A = {10, 20, 30} # set B = [40, 50] # list C = (30, 40) # tuple  print(A.isdisjoint(B)) # True print(A.isdisjoint(C)) # False
Enter fullscreen mode Exit fullscreen mode

issubset() can check if every element in the set is in other as shown below:

*Memo:

  • The 1st argument is other(Required-Type:Iterable):
    • Don't use other=.
  • <= also does issubset() but <= doesn't support the combination of a set and list, tuple or iterator. 
A = {10, 20, 30} B = {10, 20, 30, 40} C = {10, 20, 30} D = {10, 20} print(A.issubset(B)) # True print(A.issubset(C)) # True print(A.issubset(D)) # False print(A <= B) # True print(A <= C) # True print(A <= D) # False
Enter fullscreen mode Exit fullscreen mode 
A = {10, 20, 30} # set B = [10, 20, 30, 40] # list C = (10, 20, 30) # tuple D = iter([10, 20]) # iterator  print(A.issubset(B)) # True print(A.issubset(C)) # True print(A.issubset(D)) # False
Enter fullscreen mode Exit fullscreen mode

issuperset() can check if every element in other is in the set as shown below:

*Memo:

  • The 1st argument is other(Optional-Type:Iterable):
    • Don't use other=.
  • >= also does issuperset() but >= doesn't support the combination of a set and list, tuple or iterator. 
A = {10, 20, 30} B = {10, 20, 30, 40} C = {10, 20, 30} D = {10, 20} print(A.issuperset(B)) # False print(A.issuperset(C)) # True print(A.issuperset(D)) # True print(A >= B) # False print(A >= C) # True print(A >= D) # True
Enter fullscreen mode Exit fullscreen mode 
A = {10, 20, 30} # set B = [10, 20, 30, 40] # list C = (10, 20, 30) # tuple D = iter([10, 20]) # iterator  print(A.issuperset(B)) # False print(A.issuperset(C)) # True print(A.issuperset(D)) # True
Enter fullscreen mode Exit fullscreen mode

sorted() can convert a set to a list, then sort the list, then the sorted list is converted to an unsorted set with set() 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:
    • Be careful, sorted() does shallow copy instead of deep copy as my issue. 
A = {3, 5, -2, 1, -4} print(sorted(A)) print(sorted(A, key=None, reverse=False)) # [-4, -2, 1, 3, 5]  print(set(sorted(A))) # {1, 3, 5, -4, -2}  print(set(sorted(A, reverse=True))) # {1, 3, 5, -4, -2}  print(set(sorted(A, key=abs))) # {1, 3, 5, -4, -2}  print(set(sorted(A, key=abs, reverse=True))) # {1, 3, 5, -4, -2}
Enter fullscreen mode Exit fullscreen mode 
A = {"apple", "Banana", "Kiwi", "cherry"} """ Case sensitive sort """ print(set(sorted(A))) # {'apple', 'cherry', 'Banana', 'Kiwi'}  """ Case insensitive sort """ print(set(sorted(A, key=str.upper))) print(set(sorted(A, key=str.lower))) # {'cherry', 'Banana', 'apple', 'Kiwi'}  """ Sort by the length of a word """ print(set(sorted(A, key=len))) # {'apple', 'cherry', 'Banana', 'Kiwi'}
Enter fullscreen mode Exit fullscreen mode

Top comments (0)