python 验证日期格式或空白

Question

我正在尝试有效的用户输入。我有不止一种有效日期，其中一种是空白的。可能有一种简单的方法可以检查这一点，但我无法弄清楚。

def check_input(i):
    valids = ['%Y-%m-%d', '%Y%M', '']
    while True:
        try:
            date = strptime(i, valids)
        except ValueError as e:
            print 'Could not parse: {}'. format(e)
        else:
            return True

我认为我无法将列表传递给 strptime 对象。它返回 TypeError: unhashable type: 'list'.

这是脚本的片段

def parse_arguments():
    parser = argparse.ArgumentParser(description='API Statistics')
    parser.add_argument('-c', '--company', help='Company name')
    parser.add_argument('-d', '--download', help='Download file', action='store_true')
    return parser.parse_args()

def list_cmds(company):
    for num, cmd in enumerate(company._cmds):
        print '{}: {}'.format(num, cmd)

def get_cmd_dict(company):
    return dict(enumerate(company._cmds))

def run_cmd(i, cmd, **kwargs):
    return getattr(i, get_cmd_dict(i)[int(cmd)])(**kwargs)

def writer(data, file):
    with open(file, 'w') as f:
        f.write(data)

def get_func_args(f):
     ins = inspect.getargspec(f).args
     ins.remove('self')
     return ins

def check_input(i):
    valids = ['%Y-%m-%d', '%Y%M', '']
    while True:
        try:
            date = strptime(i, valids)
        except ValueError as e:
            print 'Could not parse: {}'. format(e)
        else:
            return True

def main():
    args = parse_arguments()

    if args.company == 'parklogic':
        i = PlAPI(11111, 'asdf', 'program', debug=False)
        pl_cmds = get_cmd_dict(i)


        print 'please select a command'
        print '-----------------------'

        list_cmds(PlAPI)

        user_cmd = raw_input('Number: ')
        print ''

        cmd_args = get_func_args(getattr(i, pl_cmds[int(user_cmd)]))
        users_args = {}
        format_mapper = {0: 'YYYY-MM-DD',
                         1: 'YYYY-MM-DD',
                         2: 'YYYY-MM-DD',
                         3: 'YYYY-MM-DD',
                         4: 'YYYYMM',
                         5: 'YYYY-MM-DD',
                         6: 'YYYY-MM-DD HH:mm:ss',
                         7: 'YYYY-MM-DD',
                         8: 'YYYY-MM-DD'}

        for arg in cmd_args:
            user_input = raw_input('Enter {} as {} or leave blank: '.format(
                                            arg, format_mapper[int(user_cmd)]))
            if check_input(user_input):
                users_args[arg] = user_input

        resp = run_cmd(i, user_cmd, **users_args)

        if args.download:
            writer(resp.read(), '{}.csv'.format(pl_cmds[int(user_cmd)]))
        else:
            print resp.read()

    if __name__ == '__main__':
        main()

Answer 1

def check_input(i):
    valids = ['%Y-%m-%d', '%Y%M', '']
    for valid in valids
        try:
            return strptime(i, valid)
        except ValueError as e:
            pass
    return False