'heroku: no default language could be detected for this app

First time using Heroku. Trying to push. I have run the command:

heroku create --buildpack heroku/python

and it displayed

$ heroku create --buildpack heroku/python
Creating app... done, glacial-reef-7599
Setting buildpack to heroku/python... done
https://glacial-reef-7599.herokuapp.com/ | https://git.heroku.com/glacial-reef-7599.git

Stack trace:

$ git push heroku master
Counting objects: 129, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (124/124), done.
Writing objects: 100% (129/129), 69.06 KiB | 0 bytes/s, done.
Total 129 (delta 22), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote:
remote:  !     No default language could be detected for this app.
remote:                         HINT: This occurs when Heroku cannot detect the buildpack to use for this application automatically.
remote:                         See https://devcenter.heroku.com/articles/buildpacks
remote:
remote:  !     Push failed
remote: Verifying deploy...
remote:
remote: !       Push rejected to pure-badlands-9125.
remote:
To https://git.heroku.com/pure-badlands-9125.git
 ! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/pure-badlands-9125.git'

I've gotta be missing something.

I have added a requirements.txt to my root directory. It looks like this:

.git
.idea
projectapp
projectname
rango
db.sqlite3
manage.py
populate_rango.py
requirements.txt

python heroku

Solution 1:^[1]

I can't remember how I fixed this but looking at the Date Modified in my files after I posted this question I created two files:

runtime.txt (thanks rurp) which contains:

python-3.5.2

Procfile which contains:

web: gunicorn projectname.wsgi --log-file -

This is a Django project and projectname.wsgi leads to a wsgi.py located at

projectname/wsgi.py

This contains:

import os
import signal

import sys
import traceback

import time
from django.core.wsgi import get_wsgi_application
from whitenoise.django import DjangoWhiteNoise

os.environ.setdefault("DJANGO_SETTINGS_MODULE", "projectname.settings")

application = get_wsgi_application()
application = DjangoWhiteNoise(application)

Solution 2:^[2]

Quick Solution

Goto heroku dashboard (https://dashboard.heroku.com/)
go inside app/project
click setting
scroll down little bit and click add build pack
select your desired buildpack (in my case i have selected heroku/nodejs).

TLDR;

Actually what heroku does is, it tries to identify what project you are deploying by looking at files in your project, such as if your project have package.json file it understands it is a nodejs project, if your project have requirements.txt file it understands it is a python project and so on, see this document to see to know what languages you can run on a heroku server

as you know to run a specific project such as a nodejs project in a computer node runtime must be installed in that computer otherwise you can not nodejs app in the computer, what heroku does it runs each of your app in a different container, it means in one container it is only one app is running and of course that container have installed nodejs, so if a container runs only one app it doesnt make sense to install all other runtimes in the container so container have only one runtime in my case it is nodejs. they have ofcourse other type of containers such as one type for python and that container have installed python runtime(of a specific version) so if my app gets installed in python container it will not work because my app in in nodejs. for this very reason somehow we need to identify the type of app in beginning to choose correct container type, mostly heroku automatically detect it but if it is failed to detect you have to tell explicitly either by going to their dashboard settings or through runtime file in your project, and as you may have noticed you have do this only once.

Solution 3:^[3]

For future references, you must ensure that you are pushing the branch with your code to heroku master.

If you branched from your master branch and all your code is on a, say, develop, push that to the heroku master.

So instead of:

git push heroku master

You would do something like:

git push heroku develop:master

This question has important details on this How to push different local Git branches to Heroku/master

Solution 4:^[4]

You need to create a runtime.txt file. On the command line, in the same folder as your requirements.txt file, enter echo "python-3.5.1" > runtime.txt. Of course, make sure to switch the 3.5.1 with whichever version of Python you are using.

Solution 5:^[5]

When deploying using Docker, ensure to set the stack of the app to container, as shown in the docs:

heroku stack:set container

Solution 6:^[6]

I had the same problem even after including runtime.txt. What worked was the inclusion of the requirements.txt

Solution 7:^[7]

In my case I was in a sub git folder. When I looked at the root .git folder - the project indeed didn't had a package.json file - so heroku could not identify the webpack

Solution 8:^[8]

Heroku’s Python support extends to the latest stable release from the Python 2.x and Python 3.x series. Today, this support extends to these specific runtimes:

python-2.7.13
python-3.6.1

try to change your python version in runtime.txt

Solution 9:^[9]

I was running a django project and for me none of the solution above worked. So finally I gave up and went to the path thats mentioned in the error and it clearly stated that heroku needs either of the below file to detect a django project:

requirements.txt
setup.py
Pipfile

I than created a requirements.txt file by copying the contents of pip freeze in the root of the project and it worked correctly.

Solution 10:^[10]

Faced this issue today and released I had named my requirements.txt as requirements.txt.txt(I literally named the file with .txt extension when it was already a text file), I also had a runtime.txt file with the content python-3.8.7.

Renaming the requirements.txt file correctly solved my issue.

I had 3 files in my root folder: code.py, requirements.txt and runtime.txt

Solution 11:^[11]

Create Pipfile file in root folder and add python version and packages required for application. check sample file here

[[source]]

url = "https://pypi.python.org/simple"
verify_ssl = true


[packages]

django = "*"
gunicorn = "*"
django-heroku = "*"


[requires]

python_version = "3.6"

Also check Configuring Django Apps for Heroku

Solution 12:^[12]

One more thing to note is to actually commit your changes to your git repo, before you can push them to Heroku. You might have a requirements.txt setup locally, but if it's not committed to your repo, git push heroku master will not be able to locate it.

Solution 13:^[13]

If you've tried some of the above answers and the problem still persists;

Ensure you are git "committing" in the right directory.

For instance, if your file structure is as follow:

/src
    /...
    manage.py
.gitignore
Pipfile/requirements.txt
Pipfile.lock
Procfile
runtime.txt

Ensure you're git adding, committing, pushing etc. from the root directory. Since we work mostly in the src/ or main_app_directory/ we tend to forget to change directory back to root before committing.

Solution 14:^[14]

Hey guys so I have been stuck on this issue for the past two days and I found the solution to my problem. The first fix was renaming

"requirement.txt" to "requirements.txt" then I removed the runtime.txt cleared buildpacks using heroku cli set the buildpack to python heroku buildpacks:set heroku/python

and Boom! it got uploaded an everything works now

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	Josh Laird
Solution 2
Solution 3
Solution 4	rurp
Solution 5	user7217806
Solution 6	Indi
Solution 7	Gal Bracha
Solution 8	TsaiKoga
Solution 9	pcsaunak
Solution 10	Amal Sunil
Solution 11	kartheek
Solution 12	litpumpk1n
Solution 13	Olamigoke Philip
Solution 14	adwitr

'heroku: no default language could be detected for this app

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