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| Pythics Documentation Release 0.5.2 Brian R. D’Urso July 14, 2015 Contents 1 Getting started 3 1.1
Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3
Running . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2
7 2.1
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2
XML/HTML File Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.3
Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3
13 4 Pythics API 15 4.1
Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.2
Matplotlib Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.3
PyQwt Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.4
Deprecated Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5
17 6 GNU Free Documentation License 29 7 Indices and Tables 39 i ii Pythics Documentation, Release 0.5.2 This document is Copyright (C) 2008 - 2013 Brian R. D’Urso Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled ‘GNU Free Documentation License’. Pythics is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. Pythics is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with Pythics. If not, see
http://www.gnu.org/licenses/ >. Pythics is based in part on the work of the Qwt project ( http://qwt.sf.net ). Contents: Contents 1 Pythics Documentation, Release 0.5.2 2 Contents CHAPTER 1 Getting started This is the primary documentation for the Python Instrument Control System, also known as Pythics. Pythics is an application for running Python code intended to be used for simple interfaces to laboratory instruments or numerical simulations. It features a simple system for making graphical user interfaces (GUIs) with useful controls and indicators, including plotting functionality. There is a clean separation between the GUI and application code with multithreading and multiprocessing support. In this way backend code does not interfere with the functionality of the GUI. Pythics attempts to robustly handle all of the complex details of writing a program with a GUI for you, allowing you to concentrate on the functionality of your program. The key goals of Pythics are: • Provide a framework which provides a highly multiprocessing environment without requiring any extra effort by the user/developer. • Provide a simple method for specifying a GUI for typical scientific applications. • Be as Pythonic as possible. – Use standard library functions whenever possible. – Minimize introduction of new special keywords, functions, or calling conventions.
The following programs and libraries are required for Pythics to run: • Python 2.6 2.6.2 or later preferred; earlier versions lack the multiprocessing package • PyQt widget toolkit for GUI, version 4.5.4 or later The following libraries are strongly recommended for basic functionality in Pythics: • NumPy
array support • matplotlib plotting library The following libraries are optional for full functionality in Pythics: • PIL
python Imaging Library - for image display support, (1.1.7 or later preferred) • PyQwt widgets for scientific and engineering applications The following additional packages may be helpful for writing scientific code for Pythics: • PyVISA
for communicating with VISA laboratory instruments • pySerial for communicating with laboratory instruments by RS-232 3 Pythics Documentation, Release 0.5.2 • SciPy for additional numerical processing routines 1.2 Installation Pythics uses Python Distutils for installation. Installers are available for some platforms. On Windows, run the installer (.exe). It will install Pythics and place a shortcut on your desktop to launch Pythics. If an installer is not available for your platform, you can install from a source distribution (.tar.gz or .zip): • Unpack the archive file. • run python setup.py install 1.3 Running To start Pythics: • On Linux, go to the pythics/pythics directory and type python pythics-run.py. • On Windows, double-click on the shortcut created on your desktop by the installer or go to the pythics/pythics directory and double-click on pythics-run.py. • You can also start pythics from the command line with options as: Usage: pythics-run.py [options] Options: -h show help text then exit -a selects startup html file -v selects verbose mode -d selects debug mode --help same as -h --app same as -a --verbose same as -v --debug same as -d 1.3.1 Using Pythics Once Pythics is running, virtual instruments (VIs) can be opened and controlled though a combination of the Pythics menus and the VI’s GUI. Interaction with an individual VI’s GUI is not covered here, because it depends on the details of VI. Here we describe the operation of Pythics through the menus, which provide basic control of VI operations. File Menu • Open... • Close • Close All • Reload • Open Workspace... 4 Chapter 1. Getting started Pythics Documentation, Release 0.5.2 • Save Workspace • Save Workspace As... • Page Setup... • Print Preview • Print... • Exit Edit Menu • Cut • Copy
• Paste • Delete
Parameters • Load Defaults • Load..._pySerial • Save As Defaults • Save As...
Pythics Documentation, Release 0.5.2 6 Chapter 1. Getting started CHAPTER 2 Programming 2.1 Overview While the underlying architecture of Pythics is generally hidden from the user, some knowledge of the structure may be helpful in understanding how to build and run programs under Pythics. When running user code, Pythics runs as a primary process which controls the GUI, and an additional process for each loaded user program, which we will refer to as a virtual instrument (VI). The GUI process itself uses multiple threads to handle the GUI and communication with the VI subprocess, while each VI has one primary thread and possibly additional timer threads in a subprocess. Each VI subprocess is actually a true separate process handled with the Python multiprocessing package. As a result, the VI subprocesses and GUI can generally run without blocking each other, and the VI subprocesses can even be distributed over multiple processors or cores as supported by the operating system. Additionally, even if one VI subprocess crashes, for example due to an error accessing low-level hardware, the Pythics GUI and other VIs should be undisturbed. Pythics handles all communication between the VI subprocesses and the GUI process, and provides means of sharing data between VIs. Writing code for a new VI in Pythics generally consists of writing two components: 1. A single XML file (a subset of XHTML) to layout the graphical user interface. 2. One or more text files containing Python code. These give functionality to the VI. The XML file is loaded by the GUI process in order to set up the interface, while the Python code files are loaded and ultimately executed in a VI subprocess. For each XML file loaded a new tab will be created in the Pythics window which holds the corresponding VI GUI and a VI subprocess which handles the associated functionality. The XML file specifies the layout for the controls in the GUI with a structure very similar to that used to describe the layout of a web page. Simple tables, styles, alignments, etc. of text and controls are supported. In the XML file, parameters may also be passed to controls to setup the behavior of the controls. The XML file can also direct Pythics to load files which contain Python code, for example in order to respond to a button press. The second VI component is one or more text files which contain Python code and are loaded based on requests in the XML file. The Python code typically takes the form of a series of Python functions with a particular format. Each function to be called from the GUI should take an indefinite number of keyword arguments. In practice, when a GUI control calls a function from one of these files, Pythics passes the function an object for each control in the GUI with a id attribute. The id attribute is used as the name of the corresponding keyword argument. Additional functions or other code may be included in the Python code files for use within a VI subprocess. It may sound complex, but the examples show that this actually a simple and effective protocol.
Pythics Documentation, Release 0.5.2 Fig. 2.1: Data flow betweeen processes and threads in Pythics. 8 Chapter 2. Programming Pythics Documentation, Release 0.5.2 2.2 XML/HTML File Format The file format which describes the GUI layout in Pythics is an XML-compliant HTML format, similar to a subset of XHTML. Elements (text, controls, etc.) within the XML file are controlled by up to three sources within the XML file in addition to the document structure itself: a cascading style sheet (CSS) which specifies element properties and element attributes. The CSS is located in a described in the section below. A nearly minimal XML document for Pythics has a head with title and style elements, and a body which contains the controls and other GUI layout elements: Hello World: surrounds the main body of the html document (everything but the document header) • , : text placed on its own line, typically used for VI or section names |
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