Calling C code

We can call C functions from Cython. The C string strlen() function is the equivalent of the Python len() function. Call this function from a Cython .pyx file by importing it as follows:

from libc.string cimport strlen 

We can then call strlen() from somewhere else in the .pyx file. The .pyx file can contain any Python code. Have a look at the cython_module.pyx file in this book's code bundle:

from collections import defaultdict 
from nltk.corpus import stopwords 
from nltk.corpus import names 
from libc.string cimport strlen 
 
sw = set(stopwords.words('english')) 
all_names = set([name.lower() for name in names.words()]) 
 
def isStopWord(w): 
     py_byte_string = w.encode('UTF-8') 
     cdef char* c_string = py_byte_string 
     truth = (w in sw) or (w in all_names) or (not w.isalpha()) or (strlen(c_string) == 1) 
     return truth 
 
def filter_sw(words): 
    return [w.lower() for w in words if not isStopWord(w.lower())] 
 
def freq_dict(words...