Digi Python程序员指南：从入门到实践

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"《Python程序员指南 - digi》是一份为使用Python进行dig开发的开发者量身定制的参考资料。这份指南详细介绍了如何在Digi设备上开始Python编程，包括基本概念、工具使用、模块参考以及示例程序。" 在Python程序员指南 - digi中，主要涵盖了以下几个关键知识点： 1. **目的**：该指南旨在帮助开发者了解Python在Digi设备上的应用，从入门到进阶，提供了一个完整的知识框架。 2. **Python简介**：简述Python语言的基础和特性，强调它作为开发工具的重要性，特别是在Digi设备上的应用。 3. **额外的Python文档**：提到了除了本指南之外，还有其他官方Python文档可供参考，以获取更全面的学习资料。 4. **入门**：通过编写"Hello, World!"的简单程序，引导读者快速上手Python编程，并介绍了如何在Digi命令行界面执行Python命令。 5. **Digi命令行中的Python命令**：详述了`python`和`set python`这两个命令的用法，前者用于执行Python脚本，后者用于配置设备的Python环境。 6. **加载Python程序到Digi设备**：提供了两种方法，一种是使用`modulefinder.py`来确定需要加载的文件，另一种是利用`digi_build_zip.py`自动构建ZIP文件，方便将程序部署到设备上。 7. **推荐的Python解释器分布**：讨论了如何最优化地在Digi设备上分发和使用Python解释器，以确保程序的稳定运行。 8. **Python模块参考**：列出了完全支持的内置模块和具有Digi特定行为的模块，如`os`、`random`、`re`、`socket`、`termios`、`thread`和`threading`、`time`、`xbee_sensor`和`zigbee`等，这些模块对于设备编程至关重要。 9. **文件系统访问**：讲解了如何在Digi设备上操作文件系统，这对于读写设备存储和管理程序文件至关重要。 10. **示例程序**：提供了GPS和端口共享两个演示程序，帮助开发者理解如何在实践中应用Python。GPS演示展示了如何处理GPS数据，而端口共享演示则说明了如何有效地管理设备端口资源。通过这份指南，Python开发者可以掌握在Digi环境下开发和运行Python应用程序的全过程，包括从编写代码、调试、打包到部署的一系列技术细节。对于想要在Digi设备上使用Python的工程师来说，这是一份非常实用且详尽的参考资料。

Loading Python Programs onto a Digi Device

As demonstrated in the hello.py example, Python programs are loaded onto the Digi

device using the Digi web interface page Applications > Python. Program files and

modules can be uploaded directly to the Digi device’s file system through this page.

However, files can be uploaded one at a time only, and there is no support for directory

manipulation. This makes adding entire libraries of modules difficult and adding

packages impossible. To address this issue, Digi provides a module called zipimport,

allowing collections of modules and packages to be included in a single upload.

To use zipimport, add all the files to be moved onto the Digi device to a file named

python.zip. By default, Digi’s embedded copy of the Python interpreter checks for the

presence of this file, and examines it when performing an import. The complete list of

files included in python.zip is provided in Appendix A.

Besides python.zip, the zipimport module can be used with additional .zip files,

provided the Python program knows of their presence and modifies its environment

accordingly. Internally, the files accessed through the Applications -> Python web page

are stored in a directory called WEB/python/. To use additional .zip files, add them to

the sys.path variable. This causes zipimport to search that file for .zip files as well. See

the GPS sample application for an example.

Using modulefinder.py to Determine Files to Load

For most programs, determining which files should be moved onto the Digi device should

be fairly simple, because most likely you are writing most program modules and content

yourself. However, when using third party modules or those provided by the standard

distribution, a tree of dependencies may exist, making it difficult to determine which files

must be placed on the device.

The standard Python distribution provides a tool called modulefinder.py that is useful in

this scenario. This tool examines imports in Python programs to build a list of modules

that may be used.

Using digi_build_zip.py to Automatically Build a zip File

digi_build_zip.py is an experimental utility to automatically build a zip file containing

modules and packages required to run a Python application on the Digi platform.

At its heart, digi_build_zip.py uses the modulefinder module to analyze a given script

to build the zip file with some added intelligence. However, this analysis method is not

perfect and errs on the side of inclusion. For example, many Python standard libraries

perform dynamic feature support detection and import further packages if the OS feature

is supported. modulefinder parses these import statements and includes packages and

code that will never be used by the application script running on the Digi platform.

Using digi_build_zip.py is simple: execute the script with the name of the application

script to be loaded on the Digi device as an argument. For example:

C:\My Project> python digi_build_zip.py my_project.py

By default, digi_build_zip.py creates a zip file using the base name of the script. For

example, my_project.py becomes my_project.zip digi_build_zip.py will normally act

silently until the zip file is written, unless any errors or warnings occur. Additional script

options are available by specifying the --help option.

For example, here is output for the re regular expression module:

Name File

---- ----

m __main__ re.py

m _sre

m array /usr/lib/python2.4/lib-

dynload/array.so

m copy_reg copy_reg.py

m sre sre.py

m sre_compile sre_compile.py

m sre_constants sre_constants.py

m sre_parse sre_parse.py

m sys

m types types.py

When using modulefinder.py, the list needs to be trimmed manually to minimize the

size of the python.zip file and keep dependencies to a minimum. modulefinder.py lists

files even if they exist in an execution path that the program will never use and would

therefore not need to be present. It also lists modules that are built-in or may be

dynamically loaded in your environment. Choosing which programs to load on the Digi

device requires care, because some files may require functionality not present on the Digi

device. Further, because Python is a dynamic run-time interpreted language, this missing

functionality may not cause errors in program execution until the code is interpreted.

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