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POPython cmd interpreter adding if statements
 

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    <p>For one of my projects I have a python program built around the python <a href="http://docs.python.org/library/cmd.html" rel="nofollow">cmd</a> class. This allowed me to craft a mini language around sql statements that I was sending to a database. Besides making it far easier to connect with python, I could do things that sql can't do. This was very important for several projects. However, I now need to add in if blocks for greater control flow.</p> <p>My current thinking is that I will just add two new commands to the language, IF and END. These set a variable which determines whether or not to skip a line. I would like to know if anyone else has done this with the cmd module, and if so, is there a standard method I'm missing? Google doesn't seem to reveal anything, and the cmd docs don't reveal anything either.</p> <p>For an idea that's similar to what I'm doing, go <a href="http://blog.fogcreek.com/cheeky-python-a-redis-cli/" rel="nofollow">here</a>. Questions and comments welcome. :)</p> <p>Hmm, a little more complicated than what I was thinking, though having python syntax would be nice. I debated building a mini language for quite some time before I finally did it. The problem primarily comes in from the external limitations. I have a bunch of "data", which is being generous, to turn into sql. This is based on other "data" that won't pass through. It's also unique to each specific "version" of the problem. Doing straight data to sql would have been my first inclination, but was not practical. </p> <p>For the curious, I spent a great deal of time going over the mini languages chapter in the art of unix programming, found <a href="http://www.catb.org/~esr/writings/taoup/html/minilanguageschapter.html" rel="nofollow">here</a>.</p> <p>If I had built the thing in pure python, I wouldn't have had the flexibility I absolutely needed for the problem set.</p>
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    1. CO"I wouldn't have had the flexibility I absolutely needed for the problem set." That can't possibly be true. Your DSL has fewer features than Python and you now require *additional* features. You still don't have a Turing Complete language in your DSL, so you are sacrificing flexibility. Also, if you rebuild it to be pure Python, you sacrifice nothing. And you gain better syntax.
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    2. COI forgot to mention this in there, but one of the major constraints is that I have to insert data into the database, then based upon data I get out, make some decisions, and insert some more data, based upon the data I got out. The mini language is mostly just a wrapper around python to the database, handling each piece of functionality as an atomic unit. I would have implemented it as just functions, but I needed to mix and match them based upon today's problem, allow for an interactive mode, handle some prework, and break the thing out of another program.
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      1. USSpencer Rathbun
    3. CO@Spencer Rathbun: Nothing changes when you switch from `cmd` to proper Python. Nothing is lost. No feature is lost. No functionality is lost. Only the syntax changes.
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