AttributeError：'NoneType'对象没有属性'startswith'，而在django中使用manage.py进行迁移

Question

我正在使用 Django 1.9.13 和 python 2.7.5 当我进行迁移时，我得到以下错误。 我检查了数据库设置，一切都可以与其他应用程序一起使用。 我想不出解决办法。

我在后端使用 mysql 数据库。 我正在使用一个从测试环境中携带的应用程序。

Traceback (most recent call last):
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/root/projects/misque/lib/python2.7/site- 
packages/django/core/management/__init__.py", line 353, in 
execute_from_command_line
utility.execute()
File "/root/projects/misque/lib/python2.7/site-p 
Packages/django/core/management/__init__.py", line 345, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/root/projects/misque/lib/python2.7/site- 
packages/django/core/management/base.py", line 348, in run_from_argv
self.execute(*args, **cmd_options)
File "/root/projects/misque/lib/python2.7/site- 
packages/django/core/management/base.py", line 398, in execute
self.check()
File "/root/projects/misque/lib/python2.7/site- 
packages/django/core/management/base.py", line 426, in check
include_deployment_checks=include_deployment_checks,
File "/root/projects/misque/lib/python2.7/site- 
packages/django/core/checks/registry.py", line 75, in run_checks
new_errors = check(app_configs=app_configs)
File "/root/projects/misque/lib/python2.7/site- 
packages/django/core/checks/model_checks.py", line 28, in check_all_models
errors.extend(model.check(**kwargs))
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/models/base.py", line 1178, in check
errors.extend(cls._check_fields(**kwargs))
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/models/base.py", line 1255, in _check_fields
errors.extend(field.check(**kwargs))
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/models/fields/__init__.py", line 925, in check
errors = super(AutoField, self).check(**kwargs)
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/models/fields/__init__.py", line 208, in check
errors.extend(self._check_backend_specific_checks(**kwargs))
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/models/fields/__init__.py", line 317, in 
_check_backend_specific_checks
return connections[db].validation.check_field(self, **kwargs)
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/backends/mysql/validation.py", line 18, in check_field
field_type = field.db_type(connection)
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/models/fields/__init__.py", line 625, in db_type
return connection.data_types[self.get_internal_type()] % data
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/__init__.py", line 36, in __getattr__
return getattr(connections[DEFAULT_DB_ALIAS], item)
File "/root/projects/misque/lib/python2.7/site- 
packages/django/utils/functional.py", line 33, in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/backends/mysql/base.py", line 184, in data_types
if self.features.supports_microsecond_precision:
File "/root/projects/misque/lib/python2.7/site- 
packages/django/utils/functional.py", line 33, in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/backends/mysql/features.py", line 53, in 
supports_microsecond_precision
return self.connection.mysql_version >= (5, 6, 4) and Database.version_info 
>= (1, 2, 5)
File "/root/projects/misque/lib/python2.7/site- 
packages/django/utils/functional.py", line 33, in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/backends/mysql/base.py", line 359, in mysql_version
with self.temporary_connection():
File "/usr/lib64/python2.7/contextlib.py", line 17, in __enter__
return self.gen.next()
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/backends/base/base.py", line 564, in temporary_connection
cursor = self.cursor()
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/backends/base/base.py", line 231, in cursor
cursor = self.make_debug_cursor(self._cursor())
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/backends/base/base.py", line 204, in _cursor
self.ensure_connection()
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/backends/base/base.py", line 199, in ensure_connection
self.connect()
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/backends/base/base.py", line 170, in connect
conn_params = self.get_connection_params()
File "/root/projects/misque/lib/python2.7/site- 
packages/django/db/backends/mysql/base.py", line 251, in 
get_connection_params
if settings_dict['HOST'].startswith('/'):
AttributeError: 'NoneType' object has no attribute 'startswith'

Mysql DB 工作正常，我可以看到 db 和表。 应用在settings.py中添加

Answer 1

我发现设置中有另一个 DATABASES 配置。我删除了那个。现在好了

Answer 2

在我的情况下，我正在从 env 文件中读取 DB Credentials，它有一些错误。当我解决这个问题时。

Answer 3

首先，注意：在 Windows 中，如果您从 .env 文件加载数据库连接变量，您可能必须使用“set”而不是“export”

在 python 中，我们有 3 种不同的方式来存储凭据并使用 Python 读取它们。

1. 将它们存储为系统变量
2. 将它们作为变量存储在您的 虚拟环境
3. 将它们存储在 .env 文件中

确保您选择最方便的方式。

创建一个全局环境变量，

export varName=varValue

确保“=”之间没有空格。如果你得到一个错误“zsh: Bad Assignment”，可能是因为'='之间的空格造成的。

例如，你可以说创建这些变量

export globalSecretUser=global_uganda
export globalSecretKey = global_famitechsolutions

访问它们

import os
print(os.environ) 
# This will print a dictionary with 
# all the global environment variables

我们可以使用字典访问方法来读取环境变量，即使用 .get() 或 [ ] 如下所示

print(os.environ.get('globalSecretUser'))
print(os.environ.get('globalSecretKey'))
'''
global_uganda
global_famitechsolutions
'''

要更新环境变量，只需再次运行导出语句 export globalSecretUser=Updated_UgandaMountainGorillas

要删除环境变量，我们使用 unset 关键字

unset globalSecretUser

需要注意的是，如果您尝试访问 Python 中的变量（不存在），您将获得 KeyError 或 None，具体取决于您用于访问字典中的值的方法。

就我而言，我在 Windows 7 上使用导出而不是设置