Iterate Through Strings As Substrings?

05 January 2022 - 1 answer

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?

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)
``````