python - Syntax explanation: .join(char for char in n if char.isalpha()), return n == n[::-1] -

def palindrome(n):     n = n.lower()     n = ''.join(char char in n if char.isalpha())     return n == n[::-1] 

1. n = ''.join(char char in n if char.isalpha())

2. return n == n[::-1]

can break syntax of these 2 lines down process process?

(char char in n if char.isalpha()) pretty says in almost-english: creates generator - kind of unrealised list, can 1 element @ time - yield every char char comes n, if char.isalpha() (i.e. char alphanumeric). thus, n = "the meth", t, h, e, m, e, t , h, in order (but not space, not alphanumeric).

string.join(iterable) can take iterable (like list, or generator), , slap string between each element. if provide empty string, smoosh elements of iterable without in between. themeth - original string cleared of not letter or number.

string[from:to:step] way of slicing substrings string (or subarrays array). can leave out part of it: "012345"[1::3] take every 3rd character staring 1st (well, 2nd if you're not computer), resulting in "14". if step negative, from , to defaults reversed, , n[::-1] means "every -1th character end start", word, reversed. "themeth"[::-1] "themeth"; "the meth" palyndrome.

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*) meth bad, m'kay? don't smoke it, don't deal it, don't deal it; here easy palyndrome.