CODEWITHSUNDEEP
pythonsymbolsdecompiling
Vishal Sagar
Vishal Sagar

Reputation: 498

Counting number of symbols in Python script

I have a Telit module which runs [Python 1.5.2+] (http://www.roundsolutions.com/techdocs/python/Easy_Script_Python_r13.pdf)!. There are certain restrictions in the number of variable, module and method names I can use (< 500), the size of each variable (16k) and amount of RAM (~ 1MB). Refer pg 113&114 for details. I would like to know how to get the number of symbols being generated, size in RAM of each variable, memory usage (stack and heap usage).

I need something similar to a map file that gets generated with gcc after the linking process which shows me each constant / variable, symbol, its address and size allocated.

Upvotes: 2

Views: 568

Answers (2)

foresightyj
foresightyj

Reputation: 2106

This post makes me recall my pain once with Telit GM862-GPS modules. My code was exactly at the point that the number of variables, strings, etc added up to the limit. Of course, I didn't know this fact by then. I added one innocent line and my program did not work any more. I drove me really crazy for two days until I look at the datasheet to find this fact.

What you are looking for might not have a good answer because the Python interpreter is not a full fledged version. What I did was to use the same local variable names as many as possible. Also I deleted doc strings for functions (those count too) and replace with #comments.

In the end, I want to say that this module is good for small applications. The python interpreter does not support threads or interrupts so your program must be a super loop. When your application gets bigger, each iteration will take longer. Eventually, you might want to switch to a faster platform.

Upvotes: 0

Ben Burns
Ben Burns

Reputation: 15216

Python is an interpreted and dynamically-typed language, so generating that kind of output is very difficult, if it's even possible. I'd imagine that the only reasonable way to get this information is to profile your code on the target interpreter.

If you're looking for a true memory map, I doubt such a tool exists since Python doesn't go through the same kind of compilation process as C or C++. Since everything is initialized and allocated at runtime as the program is parsed and interpreted, there's nothing to say that one interpreter will behave the same as another, especially in a case such as this where you're running on such a different architecture. As a result, there's nothing to say that your objects will be created in the same locations or even with the same overall memory structure.

If you're just trying to determine memory footprint, you can do some manual checking with sys.getsizeof(object, [default]) provided that it is supported with Telit's libs. I don't think they're using a straight implementation of CPython. Even still, this doesn't always work and with raise a TypeError when an object's size cannot be determined if you don't specify the default parameter.

You might also get some interesting results by studying the output of the dis module's bytecode disassembly, but that assumes that dis works on your interpreter, and that your interpreter is actually implemented as a VM.

If you just want a list of symbols, take a look at this recipe. It uses reflection to dump a list of symbols.

Good manual testing is key here. Your best bet is to set up the module's CMUX (COM port MUXing), and watch the console output. You'll know very quickly if you start running out of memory.

Upvotes: 1

Related Questions