Question

I’m have this function:

def ngrams(word):
    for i in range(1, len(word) + 1):
        yield word[:i]

..and I got an error

2012-03-09 19:37:31,928 ERROR worker-bootstrap: Error running worker process
net.grinder.scriptengine.jython.JythonScriptExecutionException: SyntaxError: ('invalid syntax', ('C:\\grinder-3.7.1\\lib
\\.\\nb-romg-file-store\\current\\grinder_test.py', 72, 15, '        yield word[:i]  '))
        (no code object) at line 0

Is there any way to make yield work? I tried the same function in jython console – if works normally.

Answer 1

In older versions of Jython, generators (functions using the yield keyword) are not available by default. You can try enabling the feature by adding

from __future__ import generators

to the top of your source file. If this doesn’t work, you’re probably out of luck and generators simply are not available in that version of Jython. In that case, you can try to simulate the behaviour using lists:

def ngrams(word):
    result = []
    for i in range(1, len(word) + 1):
        result.append(word[:i])
    return result

This is dead ugly, but it should work even in the most ancient Python implementations.