将字典附加到 JSON Python 烧瓶

Question

作为编码和制作自己的小项目的新手，我终于遇到了一个困扰我的问题。

所以基本上我想做的是将我的字典附加到列表中，然后将其转储到 json 文件中。

username = request.form["username"]
password = request.form["password"]
checkbox2 = request.form["checkbox2"]
userDict = {
"username" : username,
"password" : password,
"checkbox2" : checkbox2,
}
print(userDict)
if os.path.exist("data.json"):
with open("data.json", "r") as f:
all_data = json.load(f)
else:
all_data = []
all_data.append(userDict)
with open("data.json", "w") as f:
json.dump(all_data, f)

这是我目前正在运行的代码。 我得到的回溯是在发送我的表单时。

json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
Traceback (most recent call last):
File "C:UsersMarcoAppDataLocalProgramsPythonPython36-32libsite- 
packagesflaskapp.py", line 2309, in __call__
return self.wsgi_app(environ, start_response)
File "C:UsersMarcoAppDataLocalProgramsPythonPython36-32libsite- 
packagesflaskapp.py", line 2295, in wsgi_app
response = self.handle_exception(e)
File "C:UsersMarcoAppDataLocalProgramsPythonPython36-32libsite- 
packagesflaskapp.py", line 1741, in handle_exception
reraise(exc_type, exc_value, tb)
File "C:UsersMarcoAppDataLocalProgramsPythonPython36-32libsite- 
packagesflask_compat.py", line 35, in reraise
raise value
File "C:UsersMarcoAppDataLocalProgramsPythonPython36-32libsite- 
packagesflaskapp.py", line 2292, in wsgi_app
response = self.full_dispatch_request()
File "C:UsersMarcoAppDataLocalProgramsPythonPython36-32libsite- 
packagesflaskapp.py", line 1815, in full_dispatch_request
rv = self.handle_user_exception(e)
File "C:UsersMarcoAppDataLocalProgramsPythonPython36-32libsite- 
packagesflaskapp.py", line 1718, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "C:UsersMarcoAppDataLocalProgramsPythonPython36-32libsite- 
packagesflask_compat.py", line 35, in reraise
raise value
File "C:UsersMarcoAppDataLocalProgramsPythonPython36-32libsite- 
packagesflaskapp.py", line 1813, in full_dispatch_request
rv = self.dispatch_request()
File "C:UsersMarcoAppDataLocalProgramsPythonPython36-32libsite- 
packagesflaskapp.py", line 1799, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "C:UsersMarcoDesktoptestserver.py", line 28, in sendinfo
all_data = json.load(f)
File "C:UsersMarcoAppDataLocalProgramsPythonPython36- 
32libjson__init__.py", line 299, in load
parse_constant=parse_constant, object_pairs_hook=object_pairs_hook, **kw)
File "C:UsersMarcoAppDataLocalProgramsPythonPython36- 
32libjson__init__.py", line 354, in loads
return _default_decoder.decode(s)
File "C:UsersMarcoAppDataLocalProgramsPythonPython36- 
32libjsondecoder.py", line 339, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File "C:UsersMarcoAppDataLocalProgramsPythonPython36- 
32libjsondecoder.py", line 357, in raw_decode
raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

如果 data.json 为空，我的预期 json 输出如下

{
"all_data": [{
"username": "test",
"password": "test2",
"checkbox2": "on"
}]
}

如果文件中已经有"all_data"：，那么我的预期输出应该是

{
"all_data": [{
"username": "test",
"password": "test2",
"checkbox2": "on"
},
{
"username": "test3",
"password": "test4",
"checkbox2": "on"
}
]
}

这个问题已经困扰了我 3 天，我认为这将是我最后的手段，因为我是那种想自己解决它的人。

提前谢谢。

Answer 1

您的data.json是否已经存在但为空？在这种情况下，JSON 库将抛出错误！您应该在 data.json 中填写类似[]的字符串以避免此错误。

Answer 2

正如 Rishav 所指出的，当文件 data.json 存在但为空时，错误来自json.load(f(语句：

if os.path.exist("data.json"):
with open("data.json", "r") as f:
all_data = json.load(f)

您不仅可以通过检查文件是否存在，还可以通过检查它是否为空来解决此问题，如下所示：

if os.path.exist("data.json") and os.path.getsize("data.json") > 0:
with open("data.json", "r") as f:
all_data = json.load(f)

然后，您的代码应按预期工作。