parson
pyparsing
parson | pyparsing | |
---|---|---|
1 | 13 | |
57 | 2,100 | |
- | 1.4% | |
2.0 | 8.3 | |
10 months ago | about 1 month ago | |
Python | Python | |
- | MIT License |
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parson
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A complete compiler and VM in 150 lines of code
That's powerful enough to conveniently write, for example, a numerical root finding program for an arbitrary arithmetic expression.
But I think that within a complexity budget of 150 lines of code you can maybe be even more ambitious than that.
The example compiler in https://github.com/darius/parson/blob/master/eg_calc_compile... is a bit more stripped down than that, but in its 32 lines of code it compiles arithmetic assignment statements to a three-address RISC-like code (though using an unbounded number of registers). https://github.com/darius/parson/blob/master/eg_calc_to_rpn.... is a 16-line version that compiles the same language to a stack machine like your tutorial example.
In 66 lines of code in https://github.com/kragen/peg-bootstrap/blob/master/peg.md I wrote an example compiler which compiles a PEG grammar into a JavaScript parser for that grammar. Admittedly those 66 lines do not include an implementation of JavaScript to run the code on. It compiles the language it's written in.
In 132 lines of code in https://github.com/kragen/stoneknifeforth/blob/master/tinybo... I wrote an example compiler which compiles a crippled Forth dialect into i386 machine code, including an ELF header so you can run the result. It also compiles the language it's written in. It also doesn't include an i386 emulator to run it on.
In 83 lines of code in http://canonical.org/~kragen/sw/dev3/neelcompiler.ml Neel Krishnaswami wrote a compiler from the untyped λ-calculus to a simple assembly language for a register machine. It also doesn't include an implementation of the assembly language.
In 18 lines of code in http://canonical.org/~kragen/sw/dev3/meta5ix.m5, a simplification of META-II, I wrote a compiler from grammar descriptions to an assembly code for a parsing-oriented virtual machine. It compiles the language it's written in. A Python interpreter for the machine is in http://canonical.org/~kragen/sw/dev3/meta5ixrun.py (109 lines of code) and a precompiled version of the compiler-compiler for bootstrapping is in http://canonical.org/~kragen/sw/dev3/meta5ix.generated.m5asm.
A slightly incompatible variant of Meta5ix which instead compiles itself to C is in http://canonical.org/~kragen/sw/dev3/meta5ix2c.m5 (133 lines of code, depending on how you count). (No C compiler is included.) The precompiled C output for bootstrapping is in http://canonical.org/~kragen/sw/dev3/meta5ix2c.c.
Meta5ix is extremely weak and limited, really only enough for a compiler front-end; it can't, for example, do the kinds of RPN tricks we're talking about above.
pyparsing
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Pyparsing 3.1.0 released
After over a year since the last release of pyparsing, I've bundled up all the bug-fixes and changes, and they are now released as pyparsing 3.1.0. Visit this link for the details.
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Need help developing an interpreter
Look into "parser combinators" for building an interpreter. There's a few ones out there, but PyParsing is one I've seen around that looks pretty nifty.
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About a month ago I posted about PRegEx, an open-source project which I had started that you can use to build RegEx patterns programmatically, which the subreddit seem to like. This prompted me to keep working on it, and one month later, PRegEx v2.0.0 is out!
I havent found a way to specify an exact character match in pyparsing - https://github.com/pyparsing/pyparsing/discussions/443
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Python toolkits
STDOUT: Lark or pyparsing
- TatSu takes grammars in variation of EBNF, outputs memoizing Python PEG parsers
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Parser Combinators in Haskell
Since it is not mentioned in the article: Python users may also want to check out pyparsing [0]. It is slightly different from Parsec/FParsec (for instance, it ignores all whitespace by default), but I think it is a really good project.
[0]: https://github.com/pyparsing/pyparsing/
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Pyparsing 3.0.x - off to a rocky start, but I think 3.0.6 looks fairly solid
Here is the page of all the new changes and features in pyparsing 3.0.
- luna is a Domain specific language that translates to regex. It's an attempt to make regex more readable.
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Recommended way to read and parse a couple thousand small files
Your pyparsing parser might benefit from a tune-up. This page has some performance tips: https://github.com/pyparsing/pyparsing/wiki/Performance-Tips.
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Script for extracting info from a SQL File
If your SQL has fairly complex structure, you will need a full blown SQL parser. If your statements are mostly simple select, you can get pretty close with Pyparsing, here is an example.
What are some alternatives?
proofs - My personal repository of formally verified mathematics.
parsita - The easiest way to parse text in Python
peg-bootstrap - A PEG that compiles itself.
parser - String parser combinators
stoneknifeforth - a tiny self-hosted Forth implementation
iregex - A way to write regex with objects instead of strings.
kefir - 🥛turkic morphology project
attoparsec - A fast Haskell library for parsing ByteStrings
PEGTL - Parsing Expression Grammar Template Library
sly - Sly Lex Yacc
konbini - Parser library for Kotlin
Lark - Lark is a parsing toolkit for Python, built with a focus on ergonomics, performance and modularity.