On 2022-03-07 17:05, Jen Kris wrote:
Thank you MRAB for your reply.
Regarding your first question, pSentence is a list. In the nltk
library, nltk.word_tokenize takes a string, so we convert sentence to
string before we call nltk.word_tokenize:
>>> sentence = " ".join(sentence)
>>> pt = nltk.word_tokenize(sentence)
>>> print(sentence)
[ Emma by Jane Austen 1816 ]
But with the C API it looks like this:
PyObject *pSentence = PySequence_GetItem(pSents, sent_count);
PyObject* str_sentence = PyObject_Str(pSentence); // Convert to string
; See what str_sentence looks like:
PyObject* repr_str = PyObject_Repr(str_sentence);
PyObject* str_str = PyUnicode_AsEncodedString(repr_str, "utf-8", "~E~");
const char *bytes_str = PyBytes_AS_STRING(str_str);
printf("REPR_String: %s\n", bytes_str);
REPR_String: "['[', 'Emma', 'by', 'Jane', 'Austen', '1816', ']']"
So the two string representations are not the same – or at least the
PyUnicode_AsEncodedString is not the same, as each item is surrounded
by single quotes.
Assuming that the conversion to bytes object for the REPR is an
accurate representation of str_sentence, it looks like I need to strip
the quotes from str_sentence before “PyObject* pWTok =
PyObject_CallFunctionObjArgs(pNltk_WTok, str_sentence, 0).”
So my questions now are (1) is there a C API function that will
convert a list to a string exactly the same way as ‘’.join, and if not
then (2) how can I strip characters from a string object in the C API?
Your Python code is joining the list with a space as the separator.
The equivalent using the C API is:
PyObject* separator;
PyObject* joined;
separator = PyUnicode_FromString(" ");
joined = PyUnicode_Join(separator, pSentence);
Py_DECREF(sep);
Mar 6, 2022, 17:42 by pyt...@mrabarnett.plus.com:
On 2022-03-07 00:32, Jen Kris via Python-list wrote:
I am using the C API in Python 3.8 with the nltk library, and
I have a problem with the return from a library call
implemented with PyObject_CallFunctionObjArgs.
This is the relevant Python code:
import nltk
from nltk.corpus import gutenberg
fileids = gutenberg.fileids()
sentences = gutenberg.sents(fileids[0])
sentence = sentences[0]
sentence = " ".join(sentence)
pt = nltk.word_tokenize(sentence)
I run this at the Python command prompt to show how it works:
sentence = " ".join(sentence)
pt = nltk.word_tokenize(sentence)
print(pt)
['[', 'Emma', 'by', 'Jane', 'Austen', '1816', ']']
type(pt)
<class 'list'>
This is the relevant part of the C API code:
PyObject* str_sentence = PyObject_Str(pSentence);
// nltk.word_tokenize(sentence)
PyObject* pNltk_WTok = PyObject_GetAttrString(pModule_mstr,
"word_tokenize");
PyObject* pWTok = PyObject_CallFunctionObjArgs(pNltk_WTok,
str_sentence, 0);
(where pModule_mstr is the nltk library).
That should produce a list with a length of 7 that looks like
it does on the command line version shown above:
['[', 'Emma', 'by', 'Jane', 'Austen', '1816', ']']
But instead the C API produces a list with a length of 24, and
the REPR looks like this:
'[\'[\', "\'", \'[\', "\'", \',\', "\'Emma", "\'", \',\',
"\'by", "\'", \',\', "\'Jane", "\'", \',\', "\'Austen", "\'",
\',\', "\'1816", "\'", \',\', "\'", \']\', "\'", \']\']'
I also tried this with PyObject_CallMethodObjArgs and
PyObject_Call without success.
Thanks for any help on this.
What is pSentence? Is it what you think it is?
To me it looks like it's either the list:
['[', 'Emma', 'by', 'Jane', 'Austen', '1816', ']']
or that list as a string:
"['[', 'Emma', 'by', 'Jane', 'Austen', '1816', ']']"
and that what you're tokenising.
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