Python error ZeroDivisionError float division by zero

Question

Hey! I am trying to create a plagiarism checker logic. I have used this from GitHub: https://github.com/abhilampard/Simple-Plagiarism-Checker

I am ending up with the following error:

ZeroDivisionError: float division by zero

Code:

from flask import Flask, request, render_template
import re
import math

app = Flask("__name__")

q = ""


@app.route("/")
def loadPage():
    return render_template('index.html', query="aws")


@app.route("/", methods=['POST'])
def cosineSimilarity():
    universalSetOfUniqueWords = []
    matchPercentage = 0

    ####################################################################################################

    inputQuery = request.form['query']
    lowercaseQuery = inputQuery.lower()

    queryWordList = re.sub("[^\w]", " ", lowercaseQuery).split()  # Replace punctuation by space and split
    queryWordList = map(str, queryWordList)

    for word in queryWordList:
        if word not in universalSetOfUniqueWords:
            universalSetOfUniqueWords.append(word)

    ####################################################################################################

    fd = open("database1.txt", "r")
    database1 = fd.read().lower()

    databaseWordList = re.sub("[^\w]", " ", database1).split()  # Replace punctuation by space and split
    databaseWordList = map(str, databaseWordList)

    for word in databaseWordList:
        if word not in universalSetOfUniqueWords:
            universalSetOfUniqueWords.append(word)

    ####################################################################################################

    queryTF = []
    databaseTF = []

    for word in universalSetOfUniqueWords:
        queryTfCounter = 0
        databaseTfCounter = 0

        for word2 in queryWordList:
            if word == word2:
                queryTfCounter += 1
        queryTF.append(queryTfCounter)

        for word2 in databaseWordList:
            if word == word2:
                databaseTfCounter += 1
        databaseTF.append(databaseTfCounter)

    dotProduct = 0
    for i in range(len(queryTF)):
        dotProduct += queryTF[i] * databaseTF[i]

    queryVectorMagnitude = 0
    for i in range(len(queryTF)):
        queryVectorMagnitude += queryTF[i] ** 2
    queryVectorMagnitude = math.sqrt(queryVectorMagnitude)

    databaseVectorMagnitude = 0
    for i in range(len(databaseTF)):
        databaseVectorMagnitude += databaseTF[i] ** 2
    databaseVectorMagnitude = math.sqrt(databaseVectorMagnitude)

    matchPercentage = (float)(dotProduct / (queryVectorMagnitude * databaseVectorMagnitude)) * 100

    '''
    print queryWordList
    print
    print databaseWordList
    print queryTF
    print
    print databaseTF
    '''

    output = "Input query text matches %0.02f%% with database." % matchPercentage

    return render_template('index.html', query=inputQuery, output=output)


app.run(debug=True)

Answer 1

remove the following statements from code
    queryWordList = map(str, queryWordList)

    databaseWordList = map(str, databaseWordList

its because map can be iterated only once and we are iterating them twice in this code
   for word in queryWordList:  and second time as
   for word2 in queryWordList:
same for databaseWordList

Hope its helps you
 

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Answer 2

The error is thrown in this line

matchPercentage = (float)(dotProduct / (queryVectorMagnitude * databaseVectorMagnitude)) * 100

if the len(databaseTF) returns 0, then databaseVectorMagnitude=0

In the above line the denominator becomes zero. A float number cannot be devided by zero. In this case the express is divided by zero, so the ZeroDivisionError: float division by zero error is thrown in the code. make sure the len(databaseTF) is greater than zero.

Otherwise add the zero check like this

if len(databaseTF) !=0 :

matchPercentage = (float)(dotProduct / (queryVectorMagnitude * databaseVectorMagnitude)) * 100