Python and Node.js on Heroku
<p>I have started to make a Node server which runs on Heroku. It was working fine until I tried to use the (unofficial) Duolingo API. I wrote the following Python script to connect to the API:</p>

<pre><code>import duolingo
import simplejson as json

lingo  = duolingo.Duolingo('harleyrowland')
print json.dumps(lingo.get_user_info())
</code></pre>

<p>and my Node server uses it using the following commands:</p>

<pre><code>var python = require('python-shell');

module.exports = {
  getData: function(callback){
    python.run('duoScript.py', function (err, results) { 
      console.log(err);
      console.log(results);
      var res = JSON.parse(results);
      var language = res.language_data.es.language_string;
      var streak = res.language_data.es.streak;
      var level = res.language_data.es.level;
      var levelPerecentage = res.language_data.es.level_percent;
      var fluency = res.language_data.es.fluency_score;
      var nextLesson = res.language_data.es.next_lesson.skill_title;
      return callback({language, streak, level, levelPerecentage, fluency, nextLesson});
    });
  }
}
</code></pre>

<p>which all works totally fine locally. </p>

<p>When I pushed this to Heroku, the code didn't work and I started to get the following error in the Heroku logs:</p>

<pre><code>{ [Error: ImportError: No module named duolingo]
     2016-10-06T00:02:32.133315+00:00 app[web.1]:   traceback: 'Traceback (most recent call last):\n  File "duoScript.py", line 1, in &lt;module&gt;\n    import duolingo\nImportError: No module named duolingo\n',
    executable: 'python',
    options: null,
    script: 'duoScript.py',
    args: null,
    exitCode: 1 
}
</code></pre>

<p>Because of this, I went on the <a href="https://devcenter.heroku.com/articles/python-pip#the-basics" rel="noreferrer">Heroku API</a> and found that I needed to add a requirements.txt file. So I did:</p>

<pre><code>duolingo-api==0.3
simplejson==3.8.2
</code></pre>

<p>which still didn't work. I then found <a href="https://stackoverflow.com/questions/36167012/node-app-with-python-module-in-project-on-heroku-not-installing">this</a> answer and added a .buildpacks file:</p>

<pre><code>https://github.com/heroku/heroku-buildpack-python.git
https://github.com/heroku/heroku-buildpack-nodejs.git
</code></pre>

<p>and I still get the same error. </p>

<p>Any idea what is causing this error?</p>

<h1>Update 1</h1>

<p>Thought I would show my Procfile too incase this was the problem:</p>

<pre><code>web: node index.js
pipinstall: pip install -r requirements.txt
</code></pre>

<h1>Update 2</h1>

<p>Output of <code>git push heroku master</code> without <code>pipinstall</code>:</p>

<pre><code>$ git push heroku master
Counting objects: 3, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (2/2), done.
Writing objects: 100% (3/3), 288 bytes | 0 bytes/s, done.
Total 3 (delta 1), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote: 
remote: -----&gt; Node.js app detected
remote: 
remote: -----&gt; Creating runtime environment
remote:        
remote:        NPM_CONFIG_LOGLEVEL=error
remote:        NPM_CONFIG_PRODUCTION=true
remote:        NODE_ENV=production
remote:        NODE_MODULES_CACHE=true
remote: 
remote: -----&gt; Installing binaries
remote:        engines.node (package.json):  5.9.1
remote:        engines.npm (package.json):   unspecified (use default)
remote:        
remote:        Downloading and installing node 5.9.1...
remote:        Using default npm version: 3.7.3
remote: 
remote: -----&gt; Restoring cache
remote:        Loading 2 from cacheDirectories (default):
remote:        - node_modules
remote:        - bower_components (not cached - skipping)
remote: 
remote: -----&gt; Building dependencies
remote:        Installing node modules (package.json)
remote: 
remote: -----&gt; Caching build
remote:        Clearing previous node cache
remote:        Saving 2 cacheDirectories (default):
remote:        - node_modules
remote:        - bower_components (nothing to cache)
remote: 
remote: -----&gt; Build succeeded!
remote:        ├── ejs@2.4.1 extraneous
remote:        ├── emailjs@1.0.8 extraneous
remote:        ├── express@4.13.3
remote:        ├── http-status@0.2.3
remote:        ├── nodemailer@1.4.0
remote:        ├── nodemailer-smtp-transport@1.0.4
remote:        ├── python-shell@0.4.0
remote:        └── xoauth2@1.2.0
remote:        
remote: -----&gt; Discovering process types
remote:        Procfile declares types -&gt; web
remote: 
remote: -----&gt; Compressing...
remote:        Done: 13M
remote: -----&gt; Launching...
remote:        Released v25
remote:        https://arcane-anchorage-33274.herokuapp.com/ deployed to Heroku
remote: 
remote: Verifying deploy... done.
</code></pre>