Set in Python (2)

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*Memos:

• My post explains a set and copy.
• My post explains the useful functions for a set (2).

add() can add an element to a set as shown below:

*Memos:

• The 1st argument is elem(Required) for an element.
• Don't use elem=.

A = {10, 30, 50} A.add(20) A.add(30) A.add(40) A.add(50) print(A) # {40, 10, 50, 20, 30} 

update() can add a set as shown below:

*Memos:

• The 1st or the later arguments are *others(Optional-Type:iterable) for zero or more iterables.
• Don't use any keywords like *others=, others=, others=, etc.
• You can use |= with sets instead of update().

A = {10, 30, 50} A.update({20, 40}) # A |= {20, 40} A.update([20, 40]) A.update((20, 40)) print(A) # {50, 20, 40, 10, 30}  A.update() print(A) # {50, 20, 40, 10, 30} 

remove() can remove a selected element from a set, giving error if the selected element doesn't exist in the set as shown below:

*Memos:

• The 1st argument is elem(Required) for an element.
• Don't use elem=.

A = {10, 30, 50} A.remove(30) print(A) # {10, 50}  A.remove(20) # KeyError: 20 

discard() can remove a selected element from a set, not giving error even if the selected element doesn't exist in the set as shown below:

*Memos:

• The 1st argument is elem(Required) for an element.
• Don't use elem=.

A = {10, 30, 50} A.discard(30) print(A) # {10, 50}  A.discard(20) print(A) # {10, 50} 

pop() can remove and throw the last element from a set as shown below. *There are no arguments:

A = {10, 30, 50} print(A.pop()) # 10 print(A) # {50, 30}  print(A.pop()) # 50 print(A) # {30}  print(A.pop()) # 30 print(A) # set()  print(A.pop()) # KeyError: 'pop from an empty set' 

clear() can remove all elements from a list. *There are no arguments:

A = {10, 30, 50} A.clear() print(A) # set()  A.clear() print(A) # set() 

union() can return all the elements of the set and *others as shown below:

*Memos:

• The 1st or the later arguments are *others(Optional-Type:iterable) for zero or more iterables.
• Don't use any keywords like *others=, others=, others=, etc.
• You can use | with sets instead of union().

A = {10, 30, 50} B = {10, 20} C = {30, 40} print(A.union(B)) # {50, 20, 10, 30} print(A.union(C)) # {50, 40, 10, 30} print(A.union(B, C)) # {50, 20, 40, 10, 30} print(A.union()) # {10, 50, 30}  print(A | B) # {50, 20, 10, 30} print(A | C) # {50, 40, 10, 30} print(A | B | C) # {50, 20, 40, 10, 30} print(A) # {10, 50, 30} 

intersection() can return the zero or more common elements of the set and *others as shown below:

*Memos:

• The 1st or the later arguments are *others(Optional-Type:iterable) for zero or more iterables.
• Don't use any keywords like *others=, others=, others=, etc.
• You can use & with sets instead of intersection().
• intersection() creates a copy while intersection_update() doesn't.

A = {10, 20, 30, 40} B = {10, 30, 50} C = {10, 20} print(A.intersection(B)) # {10, 30} print(A.intersection(C)) # {10, 20} print(A.intersection(B, C)) # {10} print(A.intersection()) # {40, 10, 20, 30}  print(A & B) # {10, 30} print(A & C) # {10, 20} print(A & B & C) # {10} print(A) # {40, 10, 20, 30} 

intersection_update() can return the zero or more common elements of the set and *others as shown below:

*Memos:

• The 1st or the later arguments are *others(Optional-Type:iterable) for zero or more iterables.
• Don't use any keywords like *others=, others=, others=, etc.
• You can use &= and & with sets instead of intersection_update().
• intersection_update() doesn't create a copy while intersection() does.

A = {10, 20, 30, 40} B = {10, 30, 50} C = {10, 20} A.intersection_update(B) # A &= B print(A) # {10, 30}  A.intersection_update(C) # A &= C print(A) # {10}  A.intersection_update(B, C) # A &= B & C print(A) # {10}  A.intersection_update() print(A) # {10}