常用字符串函数的自定义函数

Question

我需要在不使用 Python 内置函数的情况下编写以下函数：

• 如果字符串都是字母字符
• 如果字符串全部大写
• 如果字符串全是数字
• 交换大小写字符
• 将所有字符转换为小写

我已经尝试了一段时间，但想不出太多。 有人有什么提示吗？

Answer 1

对于其中的大多数，我使用 ASCII 值进行逻辑和转换。

def is_up_case(string):
    """Shows whether or not all characters in a string are uppercase"""
    for character in string:
        if not (65 <= ord(character) <= 90) and (character != " "):  # only allows capital letters and spaces
            return False
    return True


def is_low_case(string):
    """Shows whether or not all characters in a string are lowercase"""
    for character in string:
        if not (97 <= ord(character) <= 122) and (character != " "):
            return False
    return True


def is_alpha(string):
    """Shows whether or not all characters in a string are alphabetical"""
    for character in string:
        if not (97 <= ord(character) <= 122) and not (65 <= ord(character) <= 90) and (character != " "):
            return False
    return True


def up_case(string):
    """Converts letters to uppercase"""
    new_str = ""
    for character in string:
        ascii_val = ord(character)
        if 97 <= ascii_val <= 122:
            ascii_val -= 32  # 32 is the distance between ASCII values of each lowercase and its uppercase companion
        new_str += chr(ascii_val)
    return new_str


def low_case(string):
    """Converts letters to lowercase"""
    new_str = ""
    for character in string:
        ascii_val = ord(character)
        if 65 <= ascii_val <= 90:
            ascii_val += 32
        new_str += chr(ascii_val)
    return new_str


def swap_case(string):
    """Swaps uppercase to lowercase and vice versa"""
    new_str = ""
    for character in string:
        ascii_val = ord(character)
        if 65 <= ascii_val <= 90:
            ascii_val += 32
        elif 97 <= ascii_val <= 122:
            ascii_val -= 32
        else:
            pass
        new_str += chr(ascii_val)
    return new_str


def is_numbers(string):  # I could have used ASCII values with this one too, but I wanted to spice it up ;)
    """Shows if all numbers in a string can be converted to integers"""
    try:
        int(string)
        return True
    except ValueError:  # if it fails to convert the whole statement into integers, it will return False
        return False  # spaces will also cause it to return as False

希望这会有所帮助！