How to check whether a sentence is correct (simple grammar check in Python)?

Question

How to check whether a sentence is valid in Python?

Examples:

I love Stackoverflow - Correct
I Stackoverflow love - Incorrect

Answer 1

There are various Web Services providing automated proofreading and grammar checking. Some have a Python library to simplify querying.

As far as I can tell, most of those tools (certainly After the Deadline and LanguageTool) are rule based. The checked text is compared with a large set of rules describing common errors. If a rule matches, the software calls it an error. If a rule does not match, the software does nothing (it cannot detect errors it does not have rules for).

After the Deadline

import ATD
ATD.setDefaultKey("your API key")
errors = ATD.checkDocument("Looking too the water. Fixing your writing typoss.")
for error in errors:
 print "%s error for: %s **%s**" % (error.type, error.precontext, error.string)
 print "some suggestions: %s" % (", ".join(error.suggestions),)

Expected output:

grammar error for: Looking **too the**
some suggestions: to the
spelling error for: writing **typoss**
some suggestions: typos

It is possible to run the server application on your own machine, 4 GB RAM is recommended.

LanguageTool

https://pypi.python.org/pypi/language-check

>>> import language_check
>>> tool = language_check.LanguageTool('en-US')
>>> text = 'A sentence with a error in the Hitchhiker’s Guide tot he Galaxy'
>>> matches = tool.check(text)

>>> matches[0].fromy, matches[0].fromx
(0, 16)
>>> matches[0].ruleId, matches[0].replacements
('EN_A_VS_AN', ['an'])
>>> matches[1].fromy, matches[1].fromx
(0, 50)
>>> matches[1].ruleId, matches[1].replacements
('TOT_HE', ['to the'])

>>> print(matches[1])
Line 1, column 51, Rule ID: TOT_HE[1]
Message: Did you mean 'to the'?
Suggestion: to the
...

>>> language_check.correct(text, matches)
'A sentence with an error in the Hitchhiker’s Guide to the Galaxy'

It is also possible to run the server side privately.

Ginger

Additionally, this is a hacky (screen scraping) library for Ginger, arguably one of the most polished free-to-use grammar checking options out there.

Microsoft Word

It should be possible to script Microsoft Word and use its grammar checking functionality.

More

There is a curated list of grammar checkers on Open Office website. Noted in comments by Patrick.