Python - how to find all intersections of two strings?

Question

How to find all intersections (also called the longest common substrings) of two strings and their positions in both strings?

For example, if S1=\"never\"

Answer 1

I'm assuming you only want substrings to match if they have the same absolute position within their respective strings. For example, "abcd", and "bcde" won't have any matches, even though both contain "bcd".

a = "address"
b = "oddness"

#matches[x] is True if a[x] == b[x]
matches = map(lambda x: x[0] == x[1], zip(list(a), list(b)))

positions = filter(lambda x: matches[x], range(len(a)))
substrings = filter(lambda x: x.find("_") == -1 and x != "","".join(map(lambda x: ["_", a[x]][matches[x]], range(len(a)))).split("_"))

positions = [1, 2, 4, 5, 6]

substrings = ['dd', 'ess']

If you only want substrings, you can squish it into one line:

filter(lambda x: x.find("_") == -1 and x != "","".join(map(lambda x: ["_", a[x]][map(lambda x: x[0] == x[1], zip(list(a), list(b)))[x]], range(len(a)))).split("_"))