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A Java parser written in Python using PLY.

Project description

plyj [![Build Status](](

plyj is a Java parser written in Python. It has the awesome [PLY] as its sole dependency.


import plyj.parser as plyj

parser = plyj.Parser()

# parse a compilation unit from a file
tree = parser.parse_file(file('/foo/bar/'))

# parse a compilation unit from a string
tree = parser.parse_string('class Foo { }')

# parse expression from string
tree = parser.parse_expression('1 / 2 * (float) 3')

# slightly bigger example: parse from an installed JDK with sources
import zipfile
srczip = zipfile.ZipFile('/usr/lib/jvm/java-6-openjdk/', mode='r')
info = srczip.getinfo('java/lang/')
srcfile =
tree = parser.parse_file(srcfile)


plyj is more or less a 1:1 translation of the grammar used in the [Java Development Tools] for Eclipse.


The grammar is complete. There may still be errors left though. It successfully parsed every source file of the Oracle JDK. A lot of bugs were found that way but for all I know there may be many more. Time will tell.


Contributions are always welcome. Depending on the type of work it may
take a little while until I get around to accepting them.

* commit test that demonstrates a bug (optional)
* commit the fix
* open pull request

The test is required but does *not* have to be provided by you. If you
do provide it, committing it first shows appropriate messages in the
pull request and makes it easier to accept via Web.


A word of caution: Since plyj is pure Python, it is quite slow. Based on my laptop (which has an i7-3517U @ 1.90 GHz) I can present the following numbers (running inside a virtual machine):

* 619 rules
* 1149 states
* ~3.28 seconds to compile the grammar
* java/util/ takes ~0.44 seconds to parse (it's quite big though)

The timings are obviously highly dependent on the used hardware. My old laptop (Core 2 Duo @ 1 GHz) took 17 and 1.8 seconds respectively.

[Java Development Tools]:

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