def reverse_middle(s, pos):
len_s = len(s)
mid = (len_s - pos) // 2
tmp = ""
for i in range(mid):
tmp += s[i]
for i in range(mid + pos - 1, mid - 1, -1):
tmp += s[i]
for i in range(mid + pos, len_s):
tmp += s[i]
return tmp
s = "abcdefg"
pos = 3
print(reverse_middle(s, pos))
'''
run:
abedcfg
'''