python - Failed to append an element to a numpy array -

i'm trying add values generated function calc_class, not working , don't know reason. i've tried use numpy.append, numpy.insert , built-in python function append unsuccessfully.

this piece of code:

def calc_class(test):     expec = []     new in test:         prob_vector = np.zeros((len(voc)), dtype=bool) #define 'true' array store class probabilities         words_in_new = new[0].split() #split new email words         words_in_new = list(set(words_in_new)) #remove duplicated words         = 0         voc_word in voc: #for each element in voc             if voc_word in words_in_new:                  prob_vector[i] = true #set ith element of prob_vector true, if voc element in word             else:                 prob_vector[i] = false #set ith element of prob_vector false, otherwise             += 1         prob_ham = 1         in range(len(prob_vector)):             if prob_vector[i] == true:                 prob_ham *= ham_class_prob[i]             else:                 prob_ham *= (1 - ham_class_prob[i])         # alternative:     np.prod(ham_class_prob[np.where(prob_vector==true)]) * np.prod(1-  ham_class_prob[np.where(prob_vector==false)])          prob_spam = 1         in range(len(prob_vector)):             if prob_vector[i] == true:                 prob_spam *= spam_class_prob[i]             else:                 prob_spam *= (1 - spam_class_prob[i])          p_spam = 0.3         p_ham = 1 - p_spam          p_spam_given_new = (prob_spam * p_spam) / (prob_spam * p_spam + prob_ham * p_ham)  # bayes theorem         print('p(spam|new_email)=', p_spam_given_new[0])         expec.append(p_spam_given_new[0])         print(expec) 

the problem print(expect) printing empty array.

you can use pdb debug (or ipdb ipython).

from pdb import set_trace 

use "set_trace()" instead of "print('p(spam|new_email)=', p_spam_given_new[0])"(third line counted end-line), run code. pause @ line, , can run python code there, such "print(p_spam_given_new)" or "p_spam_given_new", can check "prob_spam", "p_spam" or other variable want check.