add vs update in set operations in python

Question

What is the difference between add and update operations in python if i just want to add a single value to the set.

a = set()
a.update([1]) #works
a.add(1) #         


        

Answer 1

I guess no one mentioned about the good resource from Hackerrank. I'd like to paste how Hackerrank mentions the difference between update and add for set in python.

Sets are unordered bag of unique values. A single set contains values of any immutable data type.

CREATING SET

myset = {1, 2} # Directly assigning values to a set

myset = set() # Initializing a set

myset = set(['a', 'b']) # Creating a set from a list

print(myset)  ===> {'a', 'b'}

MODIFYING SET - add() and update()

myset.add('c')

myset  ===>{'a', 'c', 'b'}

myset.add('a') # As 'a' already exists in the set, nothing happens

myset.add((5, 4))

print(myset) ===> {'a', 'c', 'b', (5, 4)} 


myset.update([1, 2, 3, 4]) # update() only works for iterable objects

print(myset) ===> {'a', 1, 'c', 'b', 4, 2, (5, 4), 3}

myset.update({1, 7, 8})

print(myset) ===>{'a', 1, 'c', 'b', 4, 7, 8, 2, (5, 4), 3}

myset.update({1, 6}, [5, 13])

print(myset) ===> {'a', 1, 'c', 'b', 4, 5, 6, 7, 8, 2, (5, 4), 13, 3}

Hope it helps. For more details on Hackerrank, here is the link.