Skip to main content

Develop Python scripts cross platform

This post was an answer to my own question:

When you write code for many moons, usually you will develop some sort of shared library/package for various projects.
These Python scripts may not be suitable for deployment as a package but you still want to use them anywhere.

Another issue is that I often need to write and run code cross platform/cluster. So I want to make sure there is an easy way to configure my code so that I don't have to modify things when I update something.

In my early attempt, I put everything into a package and use the following method to use them in any source code:

With these global variables, now I can import any function within the package:

This seems to work well at the beginning, however, I have to copy/paste this about 20 lines of code in lots of functions. And if I want to add new capability, I have to modify all of them!

So I am on a new quest to fix it.

After digging a little bit, I was able to find a better solution. So instead of defining these system wide or global variables in production code, I can place them into a standalone module.
After that, I only need to import them using 3 or 4 lines:

The magic here is that I added one single line in my bash profile.
With the combination of environment variable "PATH" and Python sys.path, I was able to import all the global variables using one single module.

With that, I can significantly reduce and clean up the code I wrote for several projects. Also, if I need to change something, I only need to change the library, nothing else.
Problem solved.



Popular posts from this blog

Spatial datasets operations: mask raster using region of interest

Climate change related studies usually involve spatial datasets extraction from a larger domain.
In this article, I will briefly discuss some potential issues and solutions.

In the most common scenario, we need to extract a raster file using a polygon based shapefile. And I will focus as an example.

In a typical desktop application such as ArcMap or ENVI, this is usually done with a tool called clip or extract using mask or ROI.

Before any analysis can be done, it is the best practice to project all datasets into the same projection.

If you are lucky enough, you may find that the polygon you will use actually matches up with the raster grid perfectly. But it rarely happens unless you created the shapefile using "fishnet" or other approaches.

What if luck is not with you? The algorithm within these tool usually will make the best estimate of the value based on the location. The nearest re-sample, but not limited to, will be used to calculate the value. But what about the outp…

Numerical simulation: ode/pde solver and spin-up

For Earth Science model development, I inevitably have to deal with ODE and PDE equations. I also have come across some discussion related to this topic, i.e.,

In an attempt to answer this question, as well as redefine the problem I am dealing with, I decided to organize some materials to illustrate our current state on this topic.

Models are essentially equations. In Earth Science, these equations are usually ODE or PDE. So I want to discuss this from a mathematical perspective.

Ideally, we want to solve these ODE/PDE with initial condition (IC) and boundary condition (BC) using various numerical methods.

Because of the nature of geology, everything is similar to its neighbors. So we can construct a system of equations which may have multiple equation for each single grid cell. Now we have an array of equation…

Watershed Delineation On A Hexagonal Mesh Grid: Part A

One of our recent publications is "Watershed Delineation On A Hexagonal Mesh Grid" published on Environmental Modeling and Software (link).
Here I want to provide some behind the scene details of this study.

(The figures are high resolution, you might need to zoom in to view.)

First, I'd like to introduce the motivation of this work. Many of us including me have done lots of watershed/catchment hydrology modeling. For example, one of my recent publications is a three-dimensional carbon-water cycle modeling work (link), which uses lots of watershed hydrology algorithms.
In principle, watershed hydrology should be applied to large spatial domain, even global scale. But why no one is doing it?  I will use the popular USDA SWAT model as an example. Why no one is setting up a SWAT model globally? 
There are several reasons we cannot use SWAT at global scale: We cannot produce a global DEM with a desired map projection. SWAT model relies on stream network, which depends on DEM.…