Linear regression - paranormal or sceptic challange

#!/usr/bin/python3
'''
Linear regression for paranormal and sceptic challange 2.0.0
In order to use train.py you need to pass two columns
label   document
splited by \t
Commands used: xzcat, paste
'''

import sys
import pickle
import random
import collections
from tokenizer import tokenize


def train():
    #Prepare
    vocabulary = set()
    word_to_index_mapping = {}
    index_to_word_mapping = {}
    word_count = collections.defaultdict(int)

    #Array x,y to use later for training process
    x = []
    y = []

    learning_rate = 0.0001

    #Read values from file
    for line in sys.stdin:
        line = line.rstrip()
        fields = line.split('\t')
        label = fields[0]
        document = fields[1]
        terms = tokenize(document)

        #Add words from document to x and label to y (we need to reconfigure label p is 1 and s is 0)
        x.append(terms)
        if label == "P":
            y.append(1)
        else:
            y.append(0)

        #Update vocabulary and count how often word appear
        for t in terms:
            word_count[t] += 1
            vocabulary.add(t)

    #Give numbers for words. Each word its own value. Indexing
    ix = 1
    for w in vocabulary:
        word_to_index_mapping[w] = ix
        index_to_word_mapping[ix] = w
        ix += 1

    #Initialize weights with random values from -1.0 to 1.0 (floats)
    weights = []
    for ix in range(0,len(vocabulary) + 1):
        weights.append(random.uniform(-1.00, 1.00))

    Loss_sum = 0.0
    Loss_sum_counter = 1

    while True:
        choose_random_example = random.randint(0,len(x)-1)
        actual_x = x[choose_random_example] #list of words
        actual_y = y[choose_random_example] #label for this set of words

        #Predict result
        y_predicted = weights[0]

        #Iterate over all words in randomly choosen example
        #With get u can avoid missing words and replace them with value u want
        #Weights replace value doesn't matter if word is missing cause word_count will give 0
        for word in actual_x:
            y_predicted += weights[word_to_index_mapping.get(word,0)] * (word_count.get(word,0) / len(word_count))

        #Cost count. Check how good was our prediction
        Loss = (y_predicted - actual_y) ** 2.0
        print(Loss_sum_counter)
        print(Loss + "\n")
        Loss_sum_counter += 1

        #Update weights
        delta = (y_predicted - actual_y) * learning_rate
        weights[0] = weights[0] - delta
        for word in actual_x:
            if word in word_to_index_mapping:
                weights[word_to_index_mapping[word]] -= ((word_count[word] / len(word_count)) * delta)

        if Loss_sum_counter > 10000:
            break


    #We save only things we need for prediction
    model = (weights, word_to_index_mapping, word_count)
    pickle.dump(model, open("model.pkl", "wb"))


train()