Classifying numbers in python

Question

I have tried to classify numbers in python from 0.0 to 1.0. However, all numbers are getting the else condition. I need each number to get the appropriate condition, but even when the number is 0.3 or 0.2 is getting the last bin. What I am doing wrong?

#!/usr/bin/python

import csv
import sys
import re

bin1=0;
bin2=0;
bin3=0;
bin4=0;
bin5=0;
bin6=0;
bin7=0;
bin8=0;
bin9=0;
bin10=0;


def Read():
     with open (file_name) as csvfile:
        readCSV = csv.reader (csvfile, delimiter=',')
        for row in readCSV:
            for num in range(1,2):
                print row[num]                
                #Include in 10 bins
                if 0.0 <= row[num] < 0.1:
                   bin1+=1;
                   print "bin1";
                elif 0.1 <= row[num] < 0.2:
                   bin2+=1;
                   print "bin2"
                elif 0.2 <= row[num] < 0.3:
                   bin3+=1;
                   print "bin3"
                elif 0.3 <= row[num] < 0.4:
                   bin4+=1;
                   print "bin4"
                elif 0.4 <= row[num] < 0.5:
                   bin5+=1;
                   print "bin5"
                elif 0.5 <= row[num] < 0.6:
                   bin6+=1;
                   print bin6;
                   print "bin6"
                elif 0.6 <= row[num] < 0.7:
                   bin7+=1;
                   print bin7;
                   print "bin7"
                elif 0.7 <= row[num] < 0.8:
                   bin8+=1;
                   print "bin8"
                elif 0.8 <= row[num] < 0.9:
                   bin9+=1;
                   print "bin9"
                else:
                   print "bin10"


file_name = str(sys.argv[1])
print file_name
Read()

What is wrong with this simple classifier?

Thank you

Cheers

score 3 · Accepted Answer · answered Dec 08 '15 at 08:35

3

It is wrong because you are reading strings from the csv file. when you compare a string to a number, then the names of their types (!!!) are compared.

Solution: convert row[num] into a number before comparing it to floating point values.

answered Dec 08 '15 at 08:35

nagylzs

3,954
6
39
70

As a side-note, you really don't need the first part of `0.1 <= row[num] < 0.2:` in any of the `elif` clauses. The nature of the `if-elif-else` construct ensures that the value is already greater or equal to 0.1 or the other values. This essentially ensures the first part to always be true. – Kendas Dec 08 '15 at 08:41
@Kendas : While correct, I find `0.3 <= num_as_float < 0.4` more elegant to read, and avoids error from moving blocks of code. – DainDwarf Dec 08 '15 at 08:42

score 1 · Answer 2 · answered Dec 08 '15 at 08:58

1

The problem is that row[num] is a string, not a number. Put the following at the top of the loop:

val = float(row[num])

Then use val in place of row[num] for any numeric operations, including comparisons.

answered Dec 08 '15 at 08:58

Tom Karzes

22,815
2
22
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Classifying numbers in python

2 Answers2