复制了有关模块和包内导入的官方Python 3教程，并且仍然收到ImportError和SystemError异常

Question

I followed Python 3 Modules tutorial and I cannot get absolute or relative intra-package imports to work.

Specifically I replicated the project structure from the tutorial. The sound folder is located in my home /home/user/ directory. All project files (excluding filters/vocoder.py and effects/surround.py ) are empty and have been generated using touch .

sound/                          Top-level package
      __init__.py               Initialize the sound package
      formats/                  Subpackage for file format conversions
              __init__.py
              wavread.py
              wavwrite.py
              aiffread.py
              aiffwrite.py
              auread.py
              auwrite.py

      effects/                  Subpackage for sound effects
              __init__.py
              echo.py
              surround.py
              reverse.py

      filters/                  Subpackage for filters
              __init__.py
              equalizer.py
              vocoder.py
              karaoke.py

As per instruction filters/vocoder.py contains:

from sound.effects import echo

When this file is executed, it results in an import error:

user@pc:~/sound$ python filters/vocoder.py
Traceback (most recent call last):
  File "filters/vocoder.py", line 1, in <module>
    from sound.effects import echo
ImportError: No module named 'sound'

user@pc:~/sound$ cd filters/

user@pc:~/sound/filters$ python vocoder.py 
Traceback (most recent call last):
  File "vocoder.py", line 1, in <module>
    from sound.effects import echo
ImportError: No module named 'sound'

Likewise I have executed each of the following lines of code in effects/surround.py separately (I commented the lines out # and rerun the script):

from . import echo
from .. import formats
from ..filters import equalizer

Which when it is executed results in:

user@pc:~/sound$ python effects/surround.py
Traceback (most recent call last):
  File "effects/surround.py", line 1, in <module>
    from . import echo
SystemError: Parent module '' not loaded, cannot perform relative import

user@pc:~/sound$ cd effects/

user@pc:~/sound/effects$ python surround.py
Traceback (most recent call last):
  File "surround.py", line 1, in <module>
    from . import echo
SystemError: Parent module '' not loaded, cannot perform relative import

What am I doing wrong, why can I not get absolute and relative imports to work in my package?

Below is a script which should help replicate the project:

mkdir ~/sound
touch ~/sound/__init__.py

mkdir ~/sound/formats
touch ~/sound/formats/__init__.py
touch ~/sound/folder/wavread.py
touch ~/sound/folder/wavwrite.py
touch ~/sound/folder/aiffread.py
touch ~/sound/folder/aiffwrite.py
touch ~/sound/folder/auread.py
touch ~/sound/folder/auwrite.py

mkdir ~/sound/effects
touch ~/sound/effects/__init__.py
touch ~/sound/folder/echo.py
touch ~/sound/folder/surround.py
touch ~/sound/folder/reverse.py

mkdir ~/sound/filters
touch ~/sound/filters/__init__.py
touch ~/sound/folder/equalizer.py
touch ~/sound/folder/vocoder.py
touch ~/sound/folder/karaoke.py


echo "from sound.effects import echo" >> ~/sound/filters/vocoder.py

echo "from . import echo" >> ~/sound/effects/surround.py
echo "from .. import formats" >> ~/sound/effects/surround.py
echo "from ..filters import equalizer" >> ~/sound/effects/surround.py

Answer 1

I was just looking at the tutorial. I don't read that from sound.effects import echo is supposed to work as is from filters/vocoders.py . What is says there in the tutorial is:

Users of the package can import individual modules from the package, for example:

import sound.effects.echo

So that would be as if a user could reference the sound directory from their current directory. Like some of the comments said, in order to do that, the user needs to either be in the same directory as sound or add the sound directory to your PATH variable. Like this:

import sys
sys.path.append( <path to sound> )
from sound.effects import echo

See also: Import a module from a relative path

Further down the tutorial, they touch on what you are trying to do, which is intra-package references . You could use this technique without adding sound to your PATH :

For example from your filters/vocoders.py module, this should work to import echo :

from ..effects import echo