Re: Flask import problem with Python 3 and __main__.py

2014-08-26 Thread Jon Ribbens 
On 2014-08-26, Terry Reedy  wrote:
> 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)

Because that's not how Flask apps work. I am showing a minimal test
case, obviously for any real app not only would __init__.py contain
more code, but there would be other files inside flaskapp/ too.
Then when deployed, 'runflaskapp.py' would either be changed or go
away entirely and the web server would just be pointed at 'flaskapp'.

>> 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.

Well, as I understand it actually the empty string is in sys.path,
which is taken by Python to mean 'the current directory'.

>> 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?

In the same directory as above, i.e. the one containing 'flaskapp'.
It clearly does find 'flaskapp' initially, otherwise I would get
a different error message "/usr/bin/python3: No module named flaskapp".

> > Unfortunately this doesn't work:
>
> Because x does not get added to sys.path.

No, but the current directory does (effectively).

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

That's no use for development though.

The important part of my question is "why is running __main__.py
from inside flaskapp/ somehow different to running runflaskapp.py
from the parent directory?" It's probably a fairly Flask-specific
question.
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Flask import problem with Python 3 and __main__.py

2014-08-26 Thread 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 
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

--
https://mail.python.org/mailman/listinfo/python-list