from collections import Counter
dict1 = {'key1':34, 'key2':89, 'key3':12, 'key4':48}
dict2 = {'key2':10, 'key3':20, 'key5':51}
combined_dict = dict(Counter(dict1) + Counter(dict2))
print(combined_dict)
'''
run:
{'key1': 34, 'key2': 99, 'key3': 32, 'key4': 48, 'key5': 51}
'''