python - Maltparser giving error in NLTK

Question

My COde is

from nltk.parse import malt
mp = malt.MaltParser(working_dir="/other/apps/maltparser-1.8.1",mco="engmalt.poly-1.7.mco",additional_java_args=['-Xmx1024m'])
print mp.raw_parse("Hello World")

And the error is

    Traceback (most recent call last):
  File "malt.py", line 13, in <module>
    print mp.raw_parse("Hello World")
  File "/usr/local/lib/python2.7/dist-packages/nltk/parse/malt.py", line 139, in raw_parse
    return self.parse(words, verbose)
  File "/usr/local/lib/python2.7/dist-packages/nltk/parse/malt.py", line 126, in parse
    return self.parse_sents([sentence], verbose)[0]
  File "/usr/local/lib/python2.7/dist-packages/nltk/parse/malt.py", line 114, in parse_sents
    return self.tagged_parse_sents(tagged_sentences, verbose)
  File "/usr/local/lib/python2.7/dist-packages/nltk/parse/malt.py", line 194, in tagged_parse_sents
    "code %d" % (' '.join(cmd), ret))
Exception: MaltParser parsing (java -Xmx1024m -jar /usr/local/bin/malt.jar -w /other/apps/maltparser-1.8.1 -c engmalt.poly-1.7.mco -i /other/apps/maltparser-1.8.1/malt_input.conlljOba1P -o /other/apps/maltparser-1.8.1/malt_output.conllPLcoTu -m parse) failed with exit code 1

Answer 1

The MaltParser API in NLTK just had a patch that fixes and stabilizes the problems that it used to have:

• How to use malt parser in python nltk
• Malt Parser throwing class not found exception
• MaltParser Not Working in Python NLTK

Here's an example of how to use MaltParser API in NLTK:

# Upgrade your NLTK.
alvas@ubi:~$ cd ~
alvas@ubi:~$ pip install -U nltk

# Get the latest MaltParser and model
alvas@ubi:~$ wget http://maltparser.org/dist/maltparser-1.8.1.zip
alvas@ubi:~$ unzip maltparser-1.8.1.zip 
alvas@ubi:~$ wget http://www.maltparser.org/mco/english_parser/engmalt.poly-1.7.mco

# In python, now you can do this:
alvas@ubi:~$ python
>>> from nltk.parse.malt import MaltParser
>>> mp = MaltParser('/home/alvas/maltparser-1.8.1', '/home/alvas/engmalt.poly-1.7.mco')
>>> sent1 = 'I shot an elephant in my pajamas .'.split()
>>> print(mp.parse_one(sent1).tree())
(shot I (elephant an (in (pajamas my))) .)

(See here for more demo code or here for a more elaborated demo code)

---

Note that you can also use the export features and you can escape the usage of full path when initializing the MaltParser object. But you have to still tell the object what is the name of the parser directory and model filename to look for, e.g.

alvas@ubi:~$ export MALT_PARSER='/home/$UID/maltparser-1.8.1/'
alvas@ubi:~$ export MALT_MODEL='/home/$UID/engmalt.poly-1.7.mco' 
alvas@ubi:~$ python
>>> from nltk.parse.malt import MaltParser
>>> mp = MaltParser('maltparser-1.8.1', 'engmalt.poly-1.7.mco')
>>> sent1 = 'I shot an elephant in my pajamas .'.split()
>>> print(mp.parse_one(sent1).tree())
(shot I (elephant an (in (pajamas my))) .)