string number average returned in string format

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

Duplicate of: https://stackoverflow.com/questions/483666/python-reverse-invert-a-mapping — nanojohn, Jul 27 '17 at 22:03
Also you can calculate your average with following code: `int(sum([num_dic[s] for s in str_split]) / len(str_split))` — Kedrzu, Jul 27 '17 at 22:06
Do you ever expect to have a word of a digit get input into your function twice? lfor example: `"two zero nine five two"` — jacoblaw, Jul 27 '17 at 22:07
To perform a lookup, rather than attempting to reverse the entire dictionary, I would use items() or iteritems() as answered [here](https://stackoverflow.com/questions/8023306/get-key-by-value-in-dictionary). That is, unless there is future value in switching the keys,values. — Andy G, Jul 27 '17 at 22:07
Possible duplicate of [Get key by value in dictionary](https://stackoverflow.com/questions/8023306/get-key-by-value-in-dictionary) — Andy G, Jul 27 '17 at 22:09
Just return `return {v: k for k, v in num_dic.items()}[int_avg]` instead of `int_avg`, note dictionaries are not intended to work this way though. — Vinícius Figueiredo, Jul 27 '17 at 22:12
Just because OP asked about reversing a dict doesn't mean it's the best solution for him. This question shouldn't be marked as a duplicate. — Sunny Patel, Jul 27 '17 at 22:18

score 1 · Answer 1 · answered Jul 27 '17 at 22:15

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

score 1 · Answer 2 · answered Jul 27 '17 at 22:17

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.

How about `return num_list[int_sum // len(str_split)]` (or worse, `return num_list[int(round(1.0 * int_sum / len(str_split)))]`) to allow it to work in both Python2 and Python 3 since OP didn't specify a version. — cdlane, Jul 28 '17 at 06:42

score 0 · Answer 3 · answered Jul 27 '17 at 22:03

0

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

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

answered Jul 27 '17 at 22:03

nanojohn

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score 0 · Answer 4 · answered Jul 27 '17 at 22:06

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

string number average returned in string format

4 Answers4