如何使用切换大小写处理异常

def safe_case_conversion(s, to_upper=True):
    if to_upper:
        return ''.join(char.upper() if char.isalpha() else char for char in s)
    else:
        return ''.join(char.lower() if char.isalpha() else char for char in s)

# 示例
input_str = "Hello, World!"
converted_str = safe_case_conversion(input_str, to_upper=True)
print(converted_str)  # 输出: HELLO, WORLD!

def safe_case_conversion(s, to_upper=True):
    if s is None:
        return None
    if to_upper:
        return s.upper()
    else:
        return s.lower()

# 示例
input_str = None
converted_str = safe_case_conversion(input_str, to_upper=True)
print(converted_str)  # 输出: None

# 使用str.translate进行高效转换
def efficient_case_conversion(s, to_upper=True):
    if to_upper:
        return s.translate(str.maketrans('abcdefghijklmnopqrstuvwxyz', 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'))
    else:
        return s.translate(str.maketrans('ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz'))

# 示例
input_str = "Hello, World!"
converted_str = efficient_case_conversion(input_str, to_upper=True)
print(converted察str)  # 输出: HELLO, WORLD!