Background

In case you are not familiar with Rubber Duck approach to solving a problem, it goes something like this :

Sometimes, if one spends enough time analyzing the problem, one can find the solution on their own. But most of the times, we don't. We get stuck and “ask” someone. Off course, that “someone” is not as familiar with the problem as you are. So in order to help you, they ask you questions (so they can understand the problem first, before they can help you) But it is often seen that when answering “them”, you come up with the solution your self.

So where does the “Rubber Duck” fit in ?

The point is, “they” didn't solve the problem, “you” did. By explaining the details. So in this case “they” might as well have been a “Rubber Duck”. You can explain the problem to a rubber duck, and will achieve the same effect. See this Wikipedia Entry for more details.

I have noticed several times, that right after I post a query on a mailing list, I will get “unstuck” myself (and I've posted answer to my own query - so that someone else might be helped in future)

So here is a recent example of how I came upon an answer by talking to a (metaphorical) rubber duck.

Problem

I was getting the following error on heroku

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app[web.1]:   File "/app/.heroku/python/lib/python3.5/site-packages/flask_mail.py", line 566, in init_app
app[web.1]:     state = self.init_mail(app.config, app.debug, app.testing)
app[web.1]:   File "/app/.heroku/python/lib/python3.5/site-packages/flask_mail.py", line 552, in init_mail
app[web.1]:     int(config.get('MAIL_DEBUG', debug)),
app[web.1]: ValueError: invalid literal for int() with base 10: 'True'

Based on the code it refers to, the error seems correct in isolation. But flask-mail documentation says (and the previous line in the stack trace also agrees) that value of app.debug is used for MAIL_DEBUG

I had set the DEBUG as follows :

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class HerokuConfig(Config):
    import os
    DEBUG = os.environ.get('DEBUG_MY_APP', False)

I've set it to True from heroku console

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$ heroku config:get DEBUG_MY_APP -s
DEBUG_MY_APP=True

But it looks like this somehow gets converted to string 'True', resulting into an error

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$ python
Python 3.4.3 (default, Apr 27 2015, 19:08:17)
Type "help", "copyright", "credits" or "license" for more information.
>>> int(True)
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>>> int('True')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: 'True'
>>>

So how do I prevent the DEBUG from turning into a string ? I think there is something obvious that I am missing.

Solution

the root cause was that os.environ.get() always returns a string. So the correct way to set DEBUG is as follows :

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class HerokuConfig(Config):
    import os
    DEBUG = os.environ.get('DEBUG_MY_APP', 'False') == 'True'

Flesch Kincaid grade level score : 2.50

Flesch Kincaid reading ease score : 92.08