Introduction

GMT is a great plotting system, which is capable of producing high quality EPS graphics.

GMT version 4 and 5 are collections of command line tools well suited to be called from shell scripts or other script languages - as in this case - Python.

The GmtPy modules aims to ease some aspects of calling GMT from Python. Additionally, it provides some helpers for autoscaling and layout management.

This version of GmtPy is compatible with GMT version 4 and 5, but not with the new GMT version 6. There are no plans to support GMT 6 from GmtPy as GMT 6 aims to provide a native interface to Python itself. However, lots of existing scripts depend on GmtPy and GMT 4/5 and we will therefore try to support this module for quite a while (writing this in 2019).

Features and design goals

  • Thin and generic wrapper to GMT command execution

    GMT commands, options and arguments are formed directly from method calls and method arguments by a clear and simple scheme. Although this attempt does not cure the ugly naming of GMT option arguments, this way it is transparent to the user and there is no need for any additional documentation to the GMT commands.

  • Plain functional wrapping, no OO interface

    Wrapping GMT into an object oriented interface would be appealing, but making it complete would require not only a lot of code, but also a vast amount of documentation. Rewriting GMT would be more straight forward, when this was the goal.

  • Portability and consistency assistance

    GmtPy uses its own consistent built-in set of GMT default parameters, such that running a GmtPy script on a different machine, or from a different user account should not change the appearance of the output graphics. But the script can of course override the GMT default parameters as needed.

  • Encapsulation and parallel execution

    GmtPy automatically maintains a temporary directory for each plot to be produced. When possible, GMT’s ‘isolation mode’ is activated and tied to the plot’s temporary directory. If used properly, this makes it painless to parallel execute several instances of a GmtPy script or to do GMT plotting in a multithreaded application.

  • GMT version selection and backward compatibility

    Parallel installations of different versions of GMT can be used. With GmtPy it is simple to select the GMT version to be used on a per plot basis.

  • Autoscaling as opt-in

    A highly configurable auto-scaler is provided. It features automatic range calculations, automatic nice tick increment determination, labeling assistance, scaled ax annotations and some convenience options such as snap-range-to-ticks, symmetric scaling and fixing the aspect ratio.

  • Layout management as opt-in

    An object oriented layout management system may be used to conveniently distribute subplots on a page. In its design, it is similar to the layout systems provided in various GUI toolkits. Different layout managers may be arbitrarily nested for further flexibility.

  • Shortcut for fixing the bounding box in the output files

  • Shortcut for PDF output