从字符串中删除首尾空格

string = "  Hello, World!  "
trimmed_string = string.strip()
print(trimmed_string)  # 输出：Hello, World!

def trim_string(string):
    start = 0
    end = len(string) - 1

    # 移动指针直到遇到非空格字符
    while start <= end and string[start] == ' ':
        start += 1
    while end >= start and string[end] == ' ':
        end -= 1

    return string[start:end+1]

string = "  Hello, World!  "
trimmed_string = trim_string(string)
print(trimmed_string)  # 输出：Hello, World!