Problem with code compatibility with Python 3.9 - "TypeError: a bytes-like object is required, not 'str'"

Question

在运行 Python 3.9 上尝试运行遥测 python 应用程序时，失败并显示错误 "TypeError: a bytes-like object is required,不是 'str'"

尝试按照其他地方的建议将 'r' 更改为 'rb'（并将 'w' 更改为 'wb'）来修复代码会导致不同的错误。

不幸的是，我无法弄清楚这一点。谁能帮我找出这里的问题？我对此很陌生。提前致谢。

  def __init__(self):
    try:
      with open(STATUS_FILE, 'r') as sfd:
        self.st_data = pickle.loads(sfd.read())
    except IOError:
      self.st_data = dict(seq=0, timestamp=int(time.time()), rx_packets=0, tx_packets=0)

    self.st_data['seq'] = (self.st_data['seq'] % 999) + 1

  def __repr__(self):
    return "%s %s" % (self.__class__, self.st_data)

  def save(self):
    self.st_data['timestamp'] = int(time.time())
    try:
      with open(STATUS_FILE, 'w') as sfd:
        sfd.write(pickle.dumps(self.st_data))
    except IOError as err:
      print(err)

Answer 1

pickle.loads() 将 bytes-like 对象作为第一个参数。你正在发送一个字符串。参见：https://docs.python.org/3/library/pickle.html#pickle.loads

此处更深入地介绍了将字符串转换为字节：Best way to convert string to bytes in Python 3?

对您来说最简单的方法可能是：

my_data = bytes(sfd.read(), 'utf-8')

Answer 2

使用二进制文件模式是正确的做法。通过这些更改使您的代码成为可重现的示例。确保删除由原始 non-working 代码创建的任何 STATUS_FILE：

STATUS_FILE = 'test.pkl'   # defined missing variable

class Test:                # added shown methods to a class
    def __init__(self):
        try:
         with open(STATUS_FILE, 'rb') as sfd:  # use binary mode
            self.st_data = pickle.loads(sfd.read())
        except IOError:
            self.st_data = dict(seq=0, timestamp=int(time.time()), rx_packets=0, tx_packets=0)

        self.st_data['seq'] = (self.st_data['seq'] % 999) + 1

    def __repr__(self):
        return "%s %s" % (self.__class__, self.st_data)

    def save(self):
        self.st_data['timestamp'] = int(time.time())
        try:
            with open(STATUS_FILE, 'wb') as sfd:   # use binary mode
                sfd.write(pickle.dumps(self.st_data))
        except IOError as err:
            print(err)

t = Test()   # instantiate class, read from save file if present
print(t)     # view the result
t.save()     # create the save file

多次运行的输出。序列增量和时间戳变化。

<class '__main__.Test'> {'seq': 1, 'timestamp': 1644104029, 'rx_packets': 0, 'tx_packets': 0}
<class '__main__.Test'> {'seq': 2, 'timestamp': 1644104029, 'rx_packets': 0, 'tx_packets': 0}
<class '__main__.Test'> {'seq': 3, 'timestamp': 1644104030, 'rx_packets': 0, 'tx_packets': 0}
<class '__main__.Test'> {'seq': 4, 'timestamp': 1644104030, 'rx_packets': 0, 'tx_packets': 0}
<class '__main__.Test'> {'seq': 5, 'timestamp': 1644104031, 'rx_packets': 0, 'tx_packets': 0}

Problem with code compatibility with Python 3.9 - "TypeError: a bytes-like object is required, not 'str'"

Problem with code compatibility with Python 3.9 - "TypeError: a bytes-like object is required, not 'str'"

python

typeerror

python-3.9