How to calculate sum of numbers separated by a special symbol?

Question

Suppose I have a string containing the following:

'*as**4fgdfgd*vv**6fdfd5***5'

String contains numbers, letters, and a special symbol such as an asterisk.

I need to find the sum of numbers (4,6) (5,5) separated by asterisk.
The number of asterisks between two numbers must be equal to 3.
Return True if sum of every pair is equal to 10.

Examples:

*as**4fgdfgd*vv**6fdfd5***5 returns True.
ssss*0***10jkj* **0***10 returns True.
5***5***5 returns True because there 3 asterisks between the numbers and sum equals 10.
8**‍‍‍‌‍‌‌‌‌‌‌‍‌‍‍‌‍‍2 returns False

My Code So far:

my_str = "*as**4fgdfgd*vv**6fdfd5***5"

my_digits = [int(x) for x in my_str if x.isnumeric()]

print(sum(my_digits))

Asked By: meallhour

||

Source

Answer 1

You can use a regex to find pairs of numbers that are separated by 3 asterisks, then convert the found numbers to int and add them, returning true if all pairs add to 10. Note that because you want overlapping matches, we need to use a lookahead as described in this question.

def all_tens(my_str):
    pairs = re.findall(r'(?=(?<!d)(d+)(?:[^*d]**){3}[^*d]*(d+))', my_str)
    return len(pairs) > 0 and all(sum(map(int, pair)) == 10 for pair in pairs)

strs = [
 '*as**4fgdfgd*vv**6fdfd5***5', 'ssss*0***10jkj* **0***10', '5***5***5', '8**‍‍‍‌‍‌‌‌‌‌‌‍‌‍‍‌‍‍2', '5***5***4'
]
for s in strs:
    print(f'{s} : {all_tens(s)}')

Output:

*as**4fgdfgd*vv**6fdfd5***5 : True
ssss*0***10jkj* **0***10 : True
5***5***5 : True
8**2 : False
5***5***4 : False

Regex explanation:

(?=(?<!d)(d+)(?:[^*d]**){3}[^*d]*(d+)(?!d))

(?= a lookahead (we use this to allow overlapping matches)
(?<!d) the preceding character must not be a digit
(d+) some digits, captured in group 1
(?:[^*d]**){3} 3 sets of an asterisk, which may be preceded by some number of characters which are neither asterisks or digits
[^*d]* some number of characters which are not asterisk or digits
(d+) some digits, captured in group 2

Answered By: Nick

How to calculate sum of numbers separated by a special symbol?

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