# 导入所需的模块
import argparse
# 创建一个解析器对象
parser = argparse.ArgumentParser(description = "An addition program")
# 添加参数
parser.add_argument("add", nargs = '*', metavar = "num", type = int,
                     help = "All the numbers separated by spaces will be added.")
# 解析来自标准输入的参数
args = parser.parse_args()
# 检查add参数是否有任何输入数据。 如果有，则打印给定数字的总和
if len(args.add) != 0:
    print(sum(args.add))

# 导入所需的模块
import os
import argparse
# 错误讯息
INVALID_FILETYPE_MSG = "Error: Invalid file format. %s must be a .txt file."
INVALID_PATH_MSG = "Error: Invalid file path/name. Path %s does not exist."
def validate_file(file_name):
    '''
    validate file name and path.
    '''
    if not valid_path(file_name):
        print(INVALID_PATH_MSG%(file_name))
        quit()
    elif not valid_filetype(file_name):
        print(INVALID_FILETYPE_MSG%(file_name))
        quit()
    return
def valid_filetype(file_name):
    # 验证文件类型
    return file_name.endswith('.txt')
def valid_path(path):
    # 验证文件路径
    return os.path.exists(path)
def read(args):
    # 获取文件名/路径
    file_name = args.read[0]
    # validate the file name/path
    validate_file(file_name)
    # 读取并打印文件内容
    with open(file_name, 'r') as f:
        print(f.read())
def show(args):
    # 获取目录路径
    dir_path = args.show[0]
    # 验证路径
    if not valid_path(dir_path):
        print("Error: No such directory found.")
        exit()
    # 获取目录中的文本文件
    files = [f for f in os.listdir(dir_path) if valid_filetype(f)]
    print("{} text files found.".format(len(files)))
    print('\n'.join(f for f in files))
def delete(args):
    # 获取文件名/路径
    file_name = args.delete[0]
    # 验证文件名/路径
    validate_file(file_name)
    # 删除文件
    os.remove(file_name)
    print("Successfully deleted {}.".format(file_name))
def copy(args):
    # 要复制的文件
    file1 = args.copy[0]
    # 要复制的文件
    file2 = args.copy[1]
    # 验证要复制的文件
    validate_file(file1)
    # 验证文件类型2
    if not valid_filetype(file2):
        print(INVALID_FILETYPE_MSG%(file2))
        exit()
    # 将file1复制到file2
    with open(file1, 'r') as f1:
        with open(file2, 'w') as f2:
            f2.write(f1.read())
    print("Successfully copied {} to {}.".format(file1, file2))
def rename(args):
    # 旧文件名
    old_filename = args.rename[0]
    # 新文件名
    new_filename = args.rename[1]
    # 验证要重命名的文件
    validate_file(old_filename)
    # 验证新文件名的类型
    if not valid_filetype(new_filename):
        print(INVALID_FILETYPE_MSG%(new_filename))
        exit()
    # 重命名
    os.rename(old_filename, new_filename)
    print("Successfully renamed {} to {}.".format(old_filename, new_filename))
def main():
    # 创建解析器对象
    parser = argparse.ArgumentParser(description = "A text file manager!")
    # 为解析器对象定义参数
    parser.add_argument("-r", "--read", type = str, nargs = 1,
                        metavar = "file_name", default = None,
                        help = "Opens and reads the specified text file.")
    parser.add_argument("-s", "--show", type = str, nargs = 1,
                        metavar = "path", default = None,
                        help = "Shows all the text files on specified directory path.\
                        Type '.' for current directory.")
    parser.add_argument("-d", "--delete", type = str, nargs = 1,
                        metavar = "file_name", default = None,
                        help = "Deletes the specified text file.")
    parser.add_argument("-c", "--copy", type = str, nargs = 2,
                        metavar = ('file1','file2'), help = "Copy file1 contents to \
                        file2 Warning: file2 will get overwritten.")
    parser.add_argument("--rename", type = str, nargs = 2,
                        metavar = ('old_name','new_name'),
                        help = "Renames the specified file to a new name.")
    # 解析来自标准输入的参数
    args = parser.parse_args()
    # 根据参数类型调用函数
    if args.read != None:
        read(args)
    elif args.show != None:
        show(args)
    elif args.delete !=None:
        delete(args)
    elif args.copy != None:
        copy(args)
    elif args.rename != None:
        rename(args)
if __name__ == "__main__":
    # 调用main函数
    main()