import string
from itertools import product, chain
from string import ascii_lowercase
from timeit import timeit
 
 
def _calc_edits1(word):
    splits = [(word[:i], word[i:]) for i in range(len(word) + 1)]
    deletes = [a + b[1:] for a, b in splits if b]
    transposes = [a + b[1] + b[0] + b[2:] for a, b in splits if len(b) > 1]
    replaces = [a + c + b[1:] for a, b in splits for c in
                string.ascii_lowercase if b]
    inserts = [a + c + b for a, b in splits for c in
               string.ascii_lowercase]
    return set(deletes + transposes + replaces + inserts)
 
 
def _split_word(word):
    return ((word[:i], word[i:]) for i in range(len(word) + 1))
 
 
def _calc_edits2(word):
    form_2, form_3, form_4 = "{}{}".format, "{}{}{}".format, "{}{}{}{}".format
 
    deletes = (form_2(a, b[1:]) for a, b in _split_word(word) if b)
    transposes = (form_4(a, b[1], b[0], b[2:])
                  for a, b in _split_word(word) if len(b) > 1)
    replaces = (form_3(a, c, b[1:]) for a, b in _split_word(word) if b for c in
                ascii_lowercase)
    inserts = (form_3(a, c, b)
               for (a, b), c in product(_split_word(word), ascii_lowercase))
 
    return set(chain(deletes, transposes, replaces, inserts))
 
 
print(timeit("_calc_edits1('Welcome')",
             "from __main__ import _calc_edits1", number=10000))
 
print(timeit("_calc_edits2('Welcome')",
             "from __main__ import _calc_edits2", number=10000))
 

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