Commit your changes or stash them before you can merge??!?!

When trying to update your local copy from remote master copy, you will see following error

$ git pull origin master
error: Your local changes to the following files would be overwritten by merge:
<list of files>
Please commit your changes or stash them before you merge.
Aborting


You have several options here

1. Commit the change
$ git add .
$ git commit -m "committing before the update"


2. Stash them
$ git stash
$ git stash pop

3. Overwrite local changes
git reset --hard

Add Twistd to your Flask app

I'm using twisted web as front end for flask wsgi app. you probably already know of it. if not, it's essential. non-blocking IO. fully scales up.

1000's of connections

essentially, twisted combines the non-blocking IO of tornado and front end container of gunicorn in one package

$ pip install twisted

$ vi run.sh
export PYTHONPATH=.:$PYTHONPATH
twistd -n web --port tcp:8006 --wsgi yourfile.app
<where .app is the flask app inside yourfile.py>

$ nohup ./run.sh &

ImportError: libGL.so.1: cannot open shared object file: No such file or directory

When I was trying to visualize a simple plot, this error: "ImportError: libGL.so.1: cannot open shared object file: No such file or directory" popped out of the blue when I was trying to debug my code.

Quick google search later, it was suggested that I use
import matplotlib
matplotlib.use("Agg")

Fine... and it did work! no more error message.... but also, i stopped seeing my plot! :)
No good.

After digging deeper, I discovered that Red Hat does not ship native OpenGL libraries, but does ship the Mesa libraries: an MIT licensed implementation of the OpenGL specification.
You can add the Mesa OpenGL runtime libraries on your system by installing the following package:

# sudo yum install mesa-libGL

Problem was solved!

Happy coding

Add github master to your project

If you have active project on your laptop and some central git already in place, follow these simple steps to add github as extra back up repo to your project.

git remote add github https://github.com/your_name/repository_name.git

# push master to github
$ git push github master

Fun with apply function in pandas

While doing some data munging, I came across one issue that had me running in circles and made me recheck my logic over and over...

I was getting duplicates in my output set while applying 'apply' function to a dataframe. More specifically, I used 'apply' function on a groupedby dataframe to process each batch of records and apply set of business rules to an external file.

Like I said, I had duplicates!

So.... the reason to this as it came apparent to me was the fact that 'apply' function needs to figure out if you were to be mutating the passed data in order to take a fast or slow path to execute the code. Hence I would have duplicate in my external file, which you won't notice if you were to apply function to the dataframe itself, in which case it would just write to it twice replacing the old same value and it would be transparent to you.

References:
https://github.com/pandas-dev/pandas/issues/7739
https://github.com/pandas-dev/pandas/issues/6753