python - 使用 PostgreSQL (psycopg2) 和 Django 运行 Python 3.4 时出错

Question

因此，如果我使用 python 启动 Python 2.7 的 shell，然后运行 ​​import psycopg2，我不会收到任何错误。但是，如果我尝试在 Python 3.4 的 shell 中运行 import psycopg2，我会得到:ImportError: No module named 'psycopg2'。另一方面，导入 django 在两个 shell 上都可以正常工作(在使用 pip3 安装它之后)。

其次，如果我运行 python3 manage.py runserver，我会得到一个错误(见下文)，而如果我只使用 python，我不会。我认为这是因为我描述的第一个问题，但我不确定(如果这是一个愚蠢的问题，我很抱歉，我真的是 Django 的新手 - 试图通过教程)。

File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/backends/postgresql_psycopg2/base.py", line 23, in < module >
import psycopg2 as Database
ImportError: No module named 'psycopg2'

During handling of the above exception, another exception occurred:

Traceback(most recent call last):
File "manage.py", line 10, in < module >
execute_from_command_line(sys.argv)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
utility.execute()
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/core/management/__init__.py", line 354, in execute
django.setup()
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/__init__.py", line 21, in setup
apps.populate(settings.INSTALLED_APPS)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/apps/registry.py", line 108, in populate
app_config.import_models(all_models)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/apps/config.py", line 202, in import_models
self.models_module = import_module(models_module_name)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/importlib/__init__.py", line 109, in import_module   
return _bootstrap._gcd_import(name[level: ], package, level)
File "<frozen importlib._bootstrap>", line 2254, in _gcd_import
File "<frozen importlib._bootstrap>", line 2237, in _find_and_load
File "<frozen importlib._bootstrap>", line 2226, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 1200, in _load_unlocked
File "<frozen importlib._bootstrap>", line 1129, in _exec
File "<frozen importlib._bootstrap>", line 1471, in exec_module
File "<frozen importlib._bootstrap>", line 321, in _call_with_frames_removed
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/contrib/auth/models.py", line 40, in < module >
class Permission(models.Model):
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/models/base.py", line 122, in __new__
new_class.add_to_class('_meta', Options(meta, * * kwargs))
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/models/base.py", line 297, in add_to_class
value.contribute_to_class(cls, name)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/models/options.py", line 166, in contribute_to_class
self.db_table = truncate_name(self.db_table, connection.ops.max_name_length())
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/__init__.py", line 40, in __getattr__
return getattr(connections[DEFAULT_DB_ALIAS], item)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/utils.py", line 242, in __getitem__
backend = load_backend(db['ENGINE'])
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/utils.py", line 108, in load_backend
return import_module('%s.base' % backend_name)
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/importlib/__init__.py", line 109, in import_module
return _bootstrap._gcd_import(name[level: ], package, level)
File "<frozen importlib._bootstrap>", line 2254, in _gcd_import
File "<frozen importlib._bootstrap>", line 2237, in _find_and_load
File "<frozen importlib._bootstrap>", line 2226, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 1200, in _load_unlocked
File "<frozen importlib._bootstrap>", line 1129, in _exec
File "<frozen importlib._bootstrap>", line 1471, in exec_module
File "<frozen importlib._bootstrap>", line 321, in _call_with_frames_removed
File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/backends/postgresql_psycopg2/base.py", line 27, in < module >
raise ImproperlyConfigured("Error loading psycopg2 module: %s" % e)
django.core.exceptions.ImproperlyConfigured: Error loading psycopg2 module: No module named 'psycopg2'

我能做些什么来修复它？

此外，我对整个 Python 2 与 3 与 Django 的业务感到非常困惑(如果这是一个非常基本的问题，再次抱歉)。当您运行 django-admin.py startproject theproject 时，如何指定要与 Django 一起使用的 Python 版本？是否只是用 Python 3 编写代码并使用 python3 而不是 python 运行所有内容一样简单？

Answer 1

确保您已经运行 pip3 install psycopg2。

默认情况下，django-admin.py 将使用 Python 2 运行。这没关系，因为它所做的只是创建项目的文件夹布局。

创建项目后，您可以编写 Python 3 代码，并使用 python3 manage.py runserver 运行您的站点以使用 Python 3。

稍后，您可能想要研究虚拟环境。如果您创建虚拟环境以使用 Python 3

virtualenv v -p python3

然后就可以运行了

./manage.py runserver

在您的虚拟环境中，它将使用 Python 3。