以字符串格式返回的平均字符串数

Question

Here are some tests:

Input: "zero nine five two"

Output: "four"

Input: "four six two three"

Ouput: "three"

Here is my code, which works until the last step where I need to inverse lookup key by value, which I dont know how to do. Any advice?

def average_string(s):
    num_dic = {'zero': 0, 'one': 1, 'two': 2, 'three': 3, 'four': 4, 'five': 5, 
    'six': 6, 'seven': 7, 'eight': 8, 'nine': 9}
    str_split = s.split()
    int_values = []
    for key, val in num_dic.items():
        if key in str_split: 
            int_values.append(val)
            int_avg = int(sum(int_values) / len(int_values))
    return int_avg

Answer 1

You can try this:

num_dic = {'zero': 0, 'one': 1, 'two': 2, 'three': 3, 'four': 4, 'five': 5, 'six': 6, 'seven': 7, 'eight': 8, 'nine': 9}

s = "zero nine five two"

new_dict = {b:a for a, b in num_dic.items()}

average = sum(num_dic[i] for i in s.split())/float(len(s.split()))

final_average = new_dict[average]

Output:

four

Answer 2

Why not just utilize a list of words to represent the numbers where the index represents their respective value?

def average_string(s):
    num_list = ['zero', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine']
    str_split = s.split()
    int_sum = sum(map(num_list.index, str_split))
    return num_list[int_sum / len(str_split)]

The map goes over each element in str_split and translates it into the numeric version by calling num_list.index() using each element as a parameter.

Finally using the same num_list , use the average value as the index to get the string version back.

Answer 3

Here is how you inverse a dictionary. This is a duplicated question though:

inv_dic = {v: k for k, v in num_dic.items()}

Answer 4

As far as I know there isn't a way to lookup in a dict by value. Instead you can loop over the dict to find the correct value like this:

for text, number in num_dic.iteritems():
    if number == int_avg:
        print text

Here is another question where you can find this: Get key by value in dictionary

You can use num_dic.items() in Python 3