dateutil syntax error while deploying Flask Application

Question

I am trying to deploy a flask application (https://github.com/ihavemadefire/BestYearYet) using Heroku. When I deploy it it crashes immediately. I can't tell if the redirect is telling me there is an error in my code (It runs perfectly on a local browser port), an error in my virtual env or if there is an error in an external library.

I have tried updating the appdirs and flask-dateutil libraries. I have tried deploying from the Heroku git cli and from Github. I checked my code to see if I missed something (but like I said, it runs fine locally) I even tried rebooting. I think this problem is beyond my experience level.

Here are the relevant error logs from Heroku (greatly truncated):

File "/app/.heroku/python/lib/python3.6/site-packages/alembic/script/base.py", line 7, in from dateutil import tz File "/app/.heroku/python/lib/python3.6/site-packages/dateutil/tz.py", line 78 self._name, ^

Have you tried to run a fresh copy of the repo in a new virtualenv? Try to mimic what Heroku does on deployment. — Thomas Howard
– Thomas Howard, Commented Apr 8, 2019 at 19:44
Simply setting python-dateutil==2.8.1 in requirements.txt solved the issue for me. Heroku was using python-dateutil==1.5.0 which seemingly had compatibility issues with python-3.6.13. Upon pushing, Heroku gave this error ERROR: heroku 0.1.4 has requirement python-dateutil==1.5, but you'll have python-dateutil 2.8.1 which is incompatible., and then showed installed python-dateutil-2.8.1 successfully. I don't know what happened here, but everything started working correctly! XD — lordparthurnaax
– lordparthurnaax, Commented Mar 12, 2021 at 13:04

Luis · Accepted Answer · 2021-01-20 01:31:59Z

4

Uninstall python-dateutil:

pip uninstall python-dateutil

And install the new version:

i use this version

pip install python-dateutil==2.81

see if you have the requirements.txt file, remember to change the version of python-dateutil there too, manually or try this:

pip freeze > requirements.txt

if you don't have a requirements.txt, consider making one because it is "good practice" and is really helpfull

answered Jan 20, 2021 at 1:31

Luis

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Joey Baker · Accepted Answer · 2019-04-08 15:39:35Z

0

It looks like alembic depends on python-dateutil. In your Requirements.txt make sure alembic comes after the dateutil entry and try pushing the app to heroku again.

answered Apr 8, 2019 at 15:39

Joey Baker

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2 Comments

ihavemadefire Over a year ago

I moved the python-dateutil above alembic and it produced the same error.

enoted Over a year ago

I had the same error. The reason is that heroku has python-dateutil==1.5.0 in the dependencies, which includes the deprecated syntax for python3.6

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