TypeError:'bytes'类型的对象不是JSON可序列化的

Question

我刚开始编程Python.我想使用scrapy来创建一个bot,它显示了TypeError:当我运行项目时,'bytes'类型的对象不是JSON可序列化的.

import json
import codecs

class W3SchoolPipeline(object):

  def __init__(self):
      self.file = codecs.open('w3school_data_utf8.json', 'wb', encoding='utf-8')

  def process_item(self, item, spider):
      line = json.dumps(dict(item)) + '\n'
      # print line

      self.file.write(line.decode("unicode_escape"))
      return item

---

from scrapy.spiders import Spider
from scrapy.selector import Selector
from w3school.items import W3schoolItem

class W3schoolSpider(Spider):

    name = "w3school"
    allowed_domains = ["w3school.com.cn"]

    start_urls = [
        "http://www.w3school.com.cn/xml/xml_syntax.asp"
    ]

    def parse(self, response):
        sel = Selector(response)
        sites = sel.xpath('//div[@id="navsecond"]/div[@id="course"]/ul[1]/li')

    items = []
    for site in sites:
        item = W3schoolItem()
        title = site.xpath('a/text()').extract()
        link = site.xpath('a/@href').extract()
        desc = site.xpath('a/@title').extract()

        item['title'] = [t.encode('utf-8') for t in title]
        item['link'] = [l.encode('utf-8') for l in link]
        item['desc'] = [d.encode('utf-8') for d in desc]
        items.append(item)
        return items

追溯:

TypeError: Object of type 'bytes' is not JSON serializable
2017-06-23 01:41:15 [scrapy.core.scraper] ERROR: Error processing       {'desc': [b'\x
e4\xbd\xbf\xe7\x94\xa8 XSLT \xe6\x98\xbe\xe7\xa4\xba XML'],
 'link': [b'/xml/xml_xsl.asp'],
 'title': [b'XML XSLT']}

Traceback (most recent call last):
File  
"c:\users\administrator\appdata\local\programs\python\python36\lib\site-p
ackages\twisted\internet\defer.py", line 653, in _runCallbacks
    current.result = callback(current.result, *args, **kw)
File "D:\LZZZZB\w3school\w3school\pipelines.py", line 19, in process_item
    line = json.dumps(dict(item)) + '\n'
File 
"c:\users\administrator\appdata\local\programs\python\python36\lib\json\_
_init__.py", line 231, in dumps
    return _default_encoder.encode(obj)
File 
"c:\users\administrator\appdata\local\programs\python\python36\lib\json\e
ncoder.py", line 199, in encode
    chunks = self.iterencode(o, _one_shot=True)
File  
"c:\users\administrator\appdata\local\programs\python\python36\lib\json\e
ncoder.py", line 257, in iterencode
    return _iterencode(o, 0)
File      
"c:\users\administrator\appdata\local\programs\python\python36\lib\
json\encoder.py", line 180, in default
    o.__class__.__name__)
  TypeError: Object of type 'bytes' is not JSON serializable

Answer 1

您bytes自己创建这些对象:

item['title'] = [t.encode('utf-8') for t in title]
item['link'] = [l.encode('utf-8') for l in link]
item['desc'] = [d.encode('utf-8') for d in desc]
items.append(item)

每个那些t.encode(),l.encode()并d.encode()呼吁创建一个bytes字符串.不要这样做,将其保留为JSON格式以序列化这些.

接下来,您正在犯其他几个错误; 在没有必要的地方编码太多了.将它留给json模块和调用处理编码返回的标准文件对象open().

您也不需要将items列表转换为字典; 它已经是一个可以直接进行JSON编码的对象:

class W3SchoolPipeline(object):    
    def __init__(self):
        self.file = open('w3school_data_utf8.json', 'w', encoding='utf-8')

    def process_item(self, item, spider):
        line = json.dumps(item) + '\n'
        self.file.write(line)
        return item

我猜你跟着一个假设Python 2的教程,你使用的是Python 3.我强烈建议你找一个不同的教程; 它不仅是为过时版本的Python编写的,如果它提倡line.decode('unicode_escape')它正在教导一些极其糟糕的习惯,这些习惯会导致难以追踪的错误.

Answer 2

简单地写<variable name>.decode("utf-8")。

例如：

myvar = b'asdqweasdasd'
myvar.decode("utf-8")

Answer 3

我今天正在处理这个问题，我知道我有一些编码为字节对象的东西，我试图用 .json 序列化为 json json.dump(my_json_object, write_to_file.json)。my_json_object在这种情况下，我创建了一个非常大的 json 对象，所以我有几个 dicts、列表和字符串要查看以查找仍然是字节格式的内容。

我最终解决它的方式：write_to_file.json将拥有导致问题的字节对象的所有内容。

在我的特殊情况下，这是通过获得的一条线

for line in text:
    json_object['line'] = line.strip()

我首先在 write_to_file.json 的帮助下找到了这个错误，然后将其更正为：

for line in text:
    json_object['line'] = line.strip().decode()