Flask import problem with Python 3 and __main__.py

[Terry Reedy]

On 8/26/2014 12:03 PM, Jon Ribbens wrote:
> Flask suggests the following file layout:
>
>      runflaskapp.py
>      flaskapp/
>          __init__.py
>
> runflaskapp.py contains:
>
>      from flaskapp import app
>      app.run(debug=True)
>
> flaskapp/__init__.py contains:
>
>      from flask import Flask
>      app = Flask(__name__)

Unless there is something else in flaskapp, this seems senseless.  Why 
not runflaskapp.py:

from flask import Flask
app = Flask(__name__)
app.run(debug=True)

> Running this with 'python3 runflaskapp.py' works fine.

You are either giving this in directory 'x' containing runflaskapp.py or 
given a longer pathname. In either case, directory 'x' get prepended to 
sys.path, so that 'import flaskapp' finds flaskapp in x.

> However it
> seems to me that a more Python3onic way of doing this would be to
> rename 'runflaskapp.py' as 'flaskapp/__main__.py'
 > and then run the whole thing as 'python3 -m flaskapp'.

In what directory?

 > Unfortunately this doesn't work:

Because x does not get added to sys.path.

>      $ python3 -m flaskapp
>       * Running on http://127.0.0.1:5000/
>       * Restarting with reloader
>      Traceback (most recent call last):
>        File "/home/username/src/flaskapp/__main__.py", line 1, in <module>
> 	from flaskapp import app
>      ImportError: No module named 'flaskapp'
>
> Does anyone know why and how to fix it?

Since flaskapp/__main__.py is found and run, make the change suggested 
above that eliminates the flaskapp import.

Or put flaskapp in site_packages, which is on the import search path .

Pip, and I presume other installers, typically puts startup scripts in a 
directory that is on the system path. For Windows, this is 
pythonxy/Scripts.  But this is more than I would do for most local apps.

-- 
Terry Jan Reedy