编写一个接受元组对象列表并返回包含所有字符串值之和的字典的函数

Question

Continue from the previous question, write a function called get_sum(tuple_list) which accepts a list of tuple objects and returns a dictionary containing the sum of values of all the strings that appear in the list. For example, if we have the following data (a list of tuple objects):

tuple_list = [('a',5), ('a',5), ('b',6), ('b',4), ('b',3), ('b',7)]

then the dictionary should contain the following:

{'a': 10, 'b': 20} My problem is how to distinguish ab value when sum them together

Test

tuple_list = [('a',5), ('a',5), ('b',6), ('b',4), ('b',3), ('b',7)]
sum_dict = get_sum(tuple_list)
for key in sorted(sum_dict.keys()):
    print("{}: {}".format(key, sum_dict[key]))

Result a: 10 b: 20

Answer 1

I would suggest to use defauldict . You can use a normal dict but it will take some more if statements.

from collections import defaultdict

d = defaultdict(int)

tuple_list = [('a',5), ('a',5), ('b',6), ('b',4), ('b',3), ('b',7)]

for a,b in tuple_list:
    d[a] +=b

print (d)

#defaultdict(<class 'int'>, {'a': 10, 'b': 20})

If you want to use your original method, you can use tuple unpacking:

def get_sum(l):
    new_dict = {}
    for x, y in l:
        if x not in new_dict:
            new_dict[x] = y
        else:
            new_dict[x] +=y
    return new_dict

print (get_sum(tuple_list))
#{'a': 10, 'b': 20}

Answer 2

A very simple solution using the standard dict 'get' method:

d={}                                                                                                                  
for c,v in tuple_list: 
    d[c]=d.get(c,0)+v

Answer 3

Try this out:

def get_sum(tuple_list):
    new_dict = {}
    for tuple in tuple_list:
        if tuple[0] not in new_dict:
            new_dict[tuple[0]] = tuple[1]
        else:
            new_dict[tuple[0]] += tuple[1]

    return new_dict


tuple_list = [('a',5), ('a',5), ('b',6), ('b',4), ('b',3), ('b',7)]
sum_dict = get_sum(tuple_list)
for key in sorted(sum_dict.keys()):
    print("{}: {}".format(key, sum_dict[key]))

If the entry is not in your list, then you make the dictionary key, value pair be the first and second indexes of the tuple. Otherwise, the key is already in the dictionary, so we simply add to its current value.