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Iterate Through Strings As Substrings?

I have a long string from which I want to read the substrings and check how many times they have occurred.

The substring count taken from the user should be used for checking the frequency.

For example:

S = "ABCDEFGHIJKLMNOPQRSTUVABCSDLSFKJJKLOP"
substringCount = 3

def foo(S):
    pass

The function should return a dictionary that looks like this,

{'ABC':2,'DEF':1,'GHI':1,'JKL':2,'MNO':1,'PQR':1 and so on...}

The length of each key is 3 as defined earlier, which can be user-defined and any number.

How do you write such a function? What is the logic for this?

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Answer

I'd probably do it through recursion, something along the line of


s = "ABCDEFGHIJKLMNOPQRSTUVABCSDLSFKJJKLOP"

userInput = int(input("Enter substring count: "))


def get_substring_count(s, userInput, res=None):
    if res is None:
        res = {}
    if len(s) == 0 or len(s) < userInput:
        return res
    tmp_s = s[:userInput]
    if tmp_s in res:
        res[tmp_s] += 1
    else:
        res[tmp_s] = 1
    return get_substring_count(s[1:], userInput, res)
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source: stackoverflow.com
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