Rapid Development Using Python

SkipWare is a series of extensions to standard Internet transport protocols that, when installed on a network device, maximizes link utilization and reliability in a stressed transmission environment. It has been developed collaboratively between GST and Comtech; GST provides the software and Comtech provides the hardware. Although SkipWare is an implementation of SCPS (space communication protocol standards), a graphical user interface is required to specify configuration settings that impact overall system performance. Given that the product forwards IP (Internet) traffic, a Web-based client was the most feasible interface for our customers.

Because the interface requirements were soft and time was short, we approached the interface with a rapid development mentality focused on constant customer feedback. A language decision had to be made, and we had the following choices (primarily due to our experience): C, PHP, Perl, Java and Python. Our selection was based upon the following criteria:

Disk space was a concern in our decision but not a driving force. The hardware provided to us was an 800MHz processor with 64MB of RAM and a 32MB root filesystem. Of those characteristics, the disk space was clearly the most precious. Because of the high clock speed and availability of RAM, interface performance was not a driving force.

Our development environment focused on customer interaction. Because time was short, the traditional approach—formal requirements gathering followed by independent development and testing—was not practical. We anticipated making changes frequently on a remote device, with a customer representative viewing the interface and providing instant feedback.

Python allowed us to achieve this environment primarily because it is easy to use interactively. Prototyping through an interactive interpreter is an effective mechanism for exploring different approaches to solving a problem. With a customer representative providing real-time feedback, we needed a language with which we could prototype a function instantly through an interactive interpreter and then copy the working function to the remote device for approval. Perl did not provide an interactive interpreter that enabled this behavior.

Our rapid development environment meant that changes had to be visible immediately to both the developer and the customer representative. Coding sessions frequently would involve work on a remote device during which time changes would be made and feedback would be gathered. Use of a compiled language inhibited our ability to prototype on a remote device, because it required maintaining a build environment. In the scenario where we changed one or two lines of code on the remote device during an interactive feedback session, we did not want to have to wait for compilation before gathering the next round of feedback. IDEs were not feasible as a solution to our problem, because much of our development occurred on the remote device.

We wanted to dispatch Web requests to code in a very direct fashion. An architecture based on a central controller that used introspection to determine where to route requests seemed a clean and simple choice. Because our controller-based architecture was abstract and generic, we had concerns about safety. Python protects the programmer from buffer overflows and has excellent reflection capabilities that can be explored at run-time. Both characteristics satisfied our needs for introspection and safety. Moreover, an inspectable run-time is nearly equivalent to running an application under a debugger while making changes. This characteristic appealed to us.

All user input arrived in string format. All output was stored in files or returned to the user in HTML format. Both of these concepts are well supported in Python. Iterating over the content of a file takes two lines of Python. In comparison, Java requires five or five instantiations followed by two or three lines to read. Once read into memory, content must be tokenized before iteration. While iterating, casting is required. The Java approach exemplifies the importance of selecting the appropriate language for your development environment—it would not have been a good language choice for the tasks we were to perform, primarily string and file manipulation. With all of its built-in types and excellent string and file manipulation, Python provided us with the tools we needed to accomplish our tasks quickly and easily (more on this later).

Narrowing down the language choices was not particularly difficult. C requires compilation, is easy to exploit through buffer overflows (and thus poses a security risk) and does not handle strings and file I/O particularly well. PHP also was dismissed because we were not accessing a database, hence many of the features of the language would not be used. Java is too bloated, requires compilation and has horrible file I/O and string manipulation.

Python survived our language elimination process because it satisfied all of our requirements. In addition to satisfying our requirements, we gravitated towards Python because of its modularity and support for objects. This allows structured code growth and accommodates change over time. We also welcomed the safety (over C) that the interpreter provides. Above all else, we selected Python as our language because it supported rapid development and our specific requirements extremely well; no other language came close in comparison. Although other languages fulfilled a subset of our requirements, no language we considered fulfilled all of the requirements better than Python.