Getting “ImportError: attempted relative import with no known parent package” when running from Python Interpreter

Question

I\'m creating a modular app using Flask blueprints feature. As a result, my directory structure is like this:

project
    __init__.py
    config.py
    mould         


        

Answer 1

I know I'm late to the party, but I think I've found a solution to this problem. Hopefully this will be useful to someone else working on a large Python project.

The trick is to try one import format and fall back to the other format if the first fails.

Approach 1

db.py

try:
    # Assume we're a sub-module in a package.
    from . import models
except ImportError:
    # Apparently no higher-level package has been imported, fall back to a local import.
    import models

On the plus side, this approach is pretty simple, but doesn't scale well (module names are duplicated). Scaling can be improved by importing programmatically.

Approach 2 (not recommended)

db.py

import importlib

root = 'project.modules.core'
my_modules = ['core', 'models']
for m in my_modules
    try:
        globals()[m] = importlib.import_module(root + '.' + m)
    except ImportError:
        globals()[m] = importlib.import_module(m)

globals() is the global symbol table.

Of course, now this functionality needs to be duplicated in every module. I'm not sure that's actually an improvement over the first approach. However, you can separate this logic out into its own independent package that lives somewhere on pythonpath.

Approach 3

package_importer.py

import importlib

def import_module(global_vars, root, modules):
    for m in modules
        try:
            global_vars[m] = importlib.import_module(root + '.' + m)
        except ImportError:
            global_vars[m] = importlib.import_module(m)

db.py

import package_importer

root = 'project.modules.core'
my_modules = ['core', 'models']
package_importer.import_module(globals(), root, my_modules)