howto find number of pairs in an array with a given sum code example

Example: Function to find a pair in an array with a given sum using hashing

def findPair(A, sum):
 
    # create an empty dictionary
    dict = {}
 
    # do for each element
    for i, e in enumerate(A):
 
        # check if pair `(e, sum-e)` exists
 
        # if the difference is seen before, print the pair
        if sum - e in dict:
            print("Pair found at index", dict.get(sum - e), "and", i)
            return
 
        # store index of the current element in the dictionary
        dict[e] = i
 
    # No pair with the given sum exists in the list
    print("Pair not found")