IMX6 Yocto构建环境下运行自定义Django项目遭遇SyntaxError的问题排查与解决

Problem Context #

I'm running a custom Django production project in a self-built IMX6 Yocto environment. Basic Django example projects run smoothly, but when I execute:

root@imx6ulevk:/home/mdwb-main# python manage.py runserver 147.106.17.9:8000

I hit a syntax error pointing to the __str__ method in my Initial_config model. The error stack traces back to this line:

return f'{self.cloud_interval} foi cadastrado com sucesso!'

I tried swapping single quotes to double quotes and removing the {self.cloud_interval} variable, but neither fix worked.

Root Cause #

The issue boils down to Python version incompatibility: Your Yocto environment uses Python 3.5, but f-strings (formatted string literals) are a feature introduced in Python 3.6. Python 3.5 doesn't recognize the f'' syntax, which triggers the SyntaxError you're seeing.

Solutions #

You have two simple, reliable ways to fix this:

1. Use str.format() (recommended for Python 3.5 compatibility)
   Replace the f-string with the older string formatting method that works in Python 3.5:

   def __str__(self):
       return '{} foi cadastrado com sucesso!'.format(self.cloud_interval)
   

2. String concatenation (functional but less clean)
   Convert the integer field to a string and concatenate it directly with your static text:

   def __str__(self):
       return str(self.cloud_interval) + ' foi cadastrado com sucesso!'
   

After applying either change, re-run the runserver command—the syntax error should be resolved.

Important Note #

Since your environment is locked to Python 3.5, make sure to avoid other Python 3.6+ features (like the walrus operator :=, instance variable type hints, etc.) in your codebase to prevent similar compatibility issues down the line.

内容的提问来源于stack exchange，提问作者enoisq