Write a Python program to find the second largest digit present in a string entered by the user.

string = input("Enter a string: ")
digits = []
for ch in string:
    if ch.isdigit():
        digits.append(int(ch))

digits = list(set(digits))

if len(digits) < 2:
    print("Second largest digit does not exist.")
else:
    digits.sort(reverse=True)
    print("Second largest digit is:", digits[1])