目标:
自写一个包,提供关于字符串和文件的模块
要求对异常可以检测


str_tools.py:

def str_reverse(s):
    """
    :param s: 传入的字符串
    :return: 反转后的字符串
    """
    # i = -1
    # j = 0
    # s2 = ""
    # while i >= (-len(s)):
    #     s2 += s[i]
    #     i -= 1
    #     j += 1
    # return s2
    return s[::-1]  # 开始:结束:步长,如果不写则是从头至尾,-1表示反着取


def str_substr(s, x, y):  # 左闭右闭
    """
    返回截取的字符串,按照左闭右闭,且非下标而是位序
    :param s: 字符串
    :param x: 起始处
    :param y: 结束处
    :return: 截取的字符串
    """
    # x-=1
    # y-=1
    # s2 = ""
    # while x <= y:
    #     s2 += s[x]
    #     x += 1
    # return s2
    return s[x - 1:y]  # 省略了:1


# 用于本文件内测试运行,但是当被导入时不会执行下面的语句
if __name__ == '__main__':
    str_reverse("测试成功")
    str_substr("测试成功", 3, 4)

file_tools.py

def openfile(path, mode, ec='utf-8'):
    try:
        opf = open(path, mode, encoding=ec)
    except FileNotFoundError as noex:
        print("＞︿＜  没有该文件,产生了报错:", noex)
    except Exception as x:
        print("（*゜ー゜*）文件存在,但是有其他问题:", x)
    else:
        return opf


"""
也可也不自写打开函数
def print_file(path):
    f=None
    try:
        f=open(path, 'r' , encoding='utf-8')
        print(f.read())
    except Exception as e:
        print("异常:",e)
    finally:
        if f:
            f.close()
"""


def print_file(path):
    f = openfile(path, 'r')
    if f:
        print(f.read())
        f.close()


def append_file(path, content):
    f = openfile(path, 'a')
    if f:
        f.write(content)
        f.close()

test.py测试文件

import my_tools.str_tools
from my_tools import file_tools

a = my_tools.str_tools.str_reverse("uestc")
print(a)  # ctseu
print(my_tools.str_tools.str_substr("uestc", 1, 3))  # ues
file_tools.print_file("飞鸟集A.txt")  # ＞︿＜  没有该文件,产生了报错: [Errno 2] No such file or directory: '飞鸟集A.txt'
file_tools.print_file("飞鸟集.txt")  # 全部打印
file_tools.append_file("飞鸟集.txt", "\nhappy")  # 追加happy