I will be working with strings approximately 365 characters in length. Within these strings, I want to find consecutive runs of the character '-' as well as the start and end index of each consecutive run. This should include instances where the character occurs only once.
Consider the following string: 'a---b-cccc-----'. I would like to know that there is a consecutive run of three '-' characters, then one occurrence, then another five '-' characters in a row. I would also like to know their start and end positions. Reporting the results in a list of tuples (start, end, number of consecutive) would be fine, e.g.:
[(1,4,3), (5,5,1), (10,14,5)]
I've considered using itertools combined with enumerate. However, I can't quite get it right. I patched this together based on previous questions, but it's missing the start index:
counts=[]
count=1
for idx, (a,b) in enumerate(itertools.zip_longest(s, s[1:], fillvalue=None)):
if a==b=="-":
count += 1
elif a!=b and a =="-":
counts.append((idx,count))
count = 1
print(counts)
Output:
[(3, 3), (5,1), (14,5)]
I pieced together the following from other questions:
g = groupby(enumerate(s), lambda x:x[1])
l = [(x[0], list(x[1])) for x in g if x[0] == '-']
[(x[1][0][0],x[1][-1][0], len(x[1])) for x in l]
Output:
[(1, 3, 3), (5, 5, 1), (10, 14, 5)]
It seems to work, but I don't particularly understand the logic of it, and I'm not sure if it will always work. Is there a better way? Or is this as efficient as it will get? I will need to be performing the search hundreds of thousands of times, so efficiency is key here.
Thanks!
One way using re.finditer:
[(*m.span(), len(m.group(0))) for m in re.finditer("-+", s)]
Output:
[(1, 4, 3), (5, 6, 1), (10, 15, 5)]