使用python:3.9镜像构建Docker容器时遭遇SyntaxError报错

问题场景 #

使用--platform=linux/amd64参数基于python:3.9镜像构建Docker容器时，启动应用触发以下语法错误：

Traceback (most recent call last):    
 File "/var/www/myapp/manage.py", line 22, in <module>       
   main()     
 File "/var/www/myapp/manage.py", line 18, in main execute_from_command_line(sys.argv)
 File "/usr/local/lib/python3.9/site-packages/django/core/management/__init__.py", line 401, in execute_from_command_line       
   utility.execute()     
 File "/usr/local/lib/python3.9/site-packages/django/core/management/__init__.py", line 345, in execute settings.INSTALLED_APPS     
 File "/usr/local/lib/python3.9/site-packages/django/conf/__init__.py", line 82, in __getattr__       self._setup(name)     
 File "/usr/local/lib/python3.9/site-packages/django/conf/__init__.py", line 69, in _setup       self._wrapped = Settings(settings_module)     
 File "/usr/local/lib/python3.9/site-packages/django/conf/__init__.py", line 170, in __init__       mod = importlib.import_module(self.SETTINGS_MODULE)     
 File "/usr/local/lib/python3.9/importlib/__init__.py", line 127, in import_module       return _bootstrap._gcd_import(name[level:], package, level)     
 File "<frozen importlib._bootstrap>", line 1030, in _gcd_import     
 File "<frozen importlib._bootstrap>", line 1007, in _find_and_load     
 File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked     
 File "<frozen importlib._bootstrap>", line 680, in _load_unlocked     
 File "<frozen importlib._bootstrap_external>", line 850, in exec_module     
 File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed     
 File "/var/www/newapp/myapp/settings.py", line 2, in <module>       
   import environ     
 File "/usr/local/lib/python3.9/site-packages/environ.py", line 114       
   raise ValueError, "No frame marked with %s." % fname                      
                   ^     

   SyntaxError: invalid syntax

尝试过的无效操作 #

修改Dockerfile中的依赖安装命令为：

• python3 -m pip install requirements.txt
• pip3 install requirements.txt

两种调整均未解决问题，容器构建仍报错退出。

问题分析 #

初步排查可能的原因：

• requirements.txt中指定的django-environ包未正确安装
• 容器内未配置虚拟环境，导致应用无法检测到已安装的依赖包

解决方法 #

在Dockerfile中添加单独的RUN命令直接安装django-environ：

RUN pip install django-environ

添加该命令后，容器构建成功，应用可正常启动。

内容的提问来源于stack exchange，提问作者1nv