如何计算一个字符在字符串中的第n次出现(位置)？

def find_nth_occurrence(string, character, n):
    count = 0
    for i in range(len(string)):
        if string[i] == character:
            count += 1
            if count == n:
                return i
    return -1

# 示例用法
string = "Hello, World!"
character = "o"
n = 2
index = find_nth_occurrence(string, character, n)
if index != -1:
    print(f"The {n}th occurrence of '{character}' is at index {index}.")
else:
    print(f"'{character}' does not occur {n} times in the string.")