python returns the second largest number method in a list

As shown below:

#  Return 1 The first in the list 2 A large number 

def second(ln):

  max = 0

  s = {}

  for i in range(len(ln)):

    flag = 0

    for j in range(len(ln)):

      if ln[i] >= ln[j] and i != j:

        flag = flag + 1

    s[i] = flag

    if flag > max:

      max = flag

  print(s)

  for i in s:

    if s[i] == max - 1:

      break


  print(ln[i])



second([1,2,7,4,5,6,8,5,3,3,9,9,10,11,5,3,20,19])