SQLAlchemy - AttributeError: type object 'JSONB' has no attribute 'lower'

10 Apr 2016 This error happened because I mistyped "db.column" instead of "db.Column" when I was creating my database model using SQLAlchemy.

This might be your problem if db.create_all() isn't creating all the columns you expected.

PHP - Problems With Long Running Processes

19 Mar 2016 Great article about the problems with using PHP for long running processes: https://software-gunslinger.tumblr.com/post/48215406921/php-is-meant-to-die-continued

Describes the main reason why I started using Python for long-running jobs.

Ansible Vault - storing secrets in repos

04 Mar 2016 When others are deploying a project for you, it's easy for mistakes to be made when secrets must be updated in environmental variables. Ansible-vault takes a different approach and encrypts the secrets - allowing you to store the secrets in your repo.

To encrypt a file: ansible-vault encrypt secrets.py
To decrypt a file: ansible-vault decrypt secrets.py

More documentation is available here: http://docs.ansible.com/ansible/playbooks_vault.html

Python - isort, useful tool for sorting python imports

04 Mar 2016 http://timothycrosley.github.io/isort/

I saw it in the django coding style documentation: https://docs.djangoproject.com/en/1.9/internals/contributing/writing-code/coding-style/

To make an entire project's imports easier to read, all you need to do is:

pip install isort
isort -rc .

There's also a sublime plugin for it here: https://github.com/thijsdezoete/sublime-text-isort-plugin#install

git commit --amend -C HEAD

19 Feb 2016 Ever committed something and needed to make changes later? Just rebase and squash it, right? Or maybe "git reset --soft HEAD~1" and commit again?

There's an even better solution: "git commit --amend -C HEAD"

It will add the combine your commit with your last commit. If you already pushed, you will need to force push your change.

pip install -e .

19 Feb 2016 I've wasted a lot of time running "python setup.py install" before testing my changes to flask-admin. It turns out you can pip install a project as "editable", which points the install toward your local directory instead of copying where the rest of your python modules are.

To install a project as editable, navigate to the repo and run "pip install -e .".

https://pip.pypa.io/en/stable/reference/pip_install/#editable-installs

Python - Dropping Into pdb From Nose

14 Feb 2016 This document describes how to drop into pdb when your Python nose tests fail: http://nose.readthedocs.org/en/latest/plugins/debug.html

It just requires running "nosetests --pdb".

Very helpful if you're debugging why a test failed.

Great Hadoop + Spark Tutorial

14 Feb 2016 This great tutorial takes you through installing hadoop and spark to analyze Reddit comment data: http://blog.insightdatalabs.com/spark-cluster-step-by-step/

Hadoop Namenode Not Starting

14 Feb 2016 My namenode was not starting because I had the wrong host configured in yarn-site.xml, mapred-site.xml, and core-site.xml.

When you're running start-dfs.sh on your namenode, ensure the line that says "starting namenode" shows "/usr/local/hadoop/logs/hadoop-ubuntu-namenode-<your namenode's hostname>.out" in the output. This is how you know your configuration is correct.

You can check your server's hostname on Ubuntu by running "echo $(hostname)".

Python - "The Darker Side of type"

26 Dec 2015 https://www.jeffknupp.com/blog/2013/12/28/improve-your-python-metaclasses-and-dynamic-classes-with-type/

That blog post has a great description of how the type keyword can be used for another purpose, creating new types.

Here's an example of the syntax: Foo = type(str('Foo'), (object, ), {})

This page has more details: http://python-3-patterns-idioms-test.readthedocs.org/en/latest/Metaprogramming.html

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