Reading from files in python

Question

I need to find out the maximum and minimum value in a line by reading a file and should be dividing the maximum value by the minimum value. Am interested to do this in python.

the contents of the file (file.txt) looks like this..

A28102_at,151,263,88,484,118,270,458,872,62,194
AB000114_at,72,21,20,61,20,85,20,25,20,65
AB000115_at,281,250,358,118,197,71,168,296,198,113

The problem am facing is i should be neglecting the first value, that is upto the first occurrence of comma and am unable to figure out a method. And also am interested to store the values in an array and then do the comparision. Is this approach correct or any better method is sugegsted?

Answer 1

As you are a beginner, I won't give a copy/paste code snippet; there is more to learn if you figure the details out yourself. But here's what you could do:

• read the file line-by-line in a loop, storing the current line in a string
• for each line, split the string on commas, resulting in a list
• drop the first element of the list
• take the maximum of the rest

Maybe someone else will come up with the actual code.

Answer 2

I'm not sure if this is the most "pythonic" way of doing it, but it should work. I'm using lists instead of arrays.

for line in fp:
    tokens = line.split(',') # tokenize the line with comma as the only delimiter
    numbers = map(int, tokens[1:]) # skip the first value and convert to integer values
    maxValue = max(numbers) # max() operates on lists or sequences, I can't recall
    minValue = min(numbers) # so does min()
    print maxValue / minValue # TADA

:)

Answer 3

Python comes with batteries! Use the csv module to parse csv files:

#!/usr/bin/env python
import csv
csvobj=csv.reader(open('file.txt','r'))
for datum in csvobj:
    datum=[float(val) for val in datum[1:]] 
    print(datum)
    maximum=max(datum)
    minimum=min(datum)
    print(maximum/minimum)

# [151.0, 263.0, 88.0, 484.0, 118.0, 270.0, 458.0, 872.0, 62.0, 194.0]
# 14.064516129
# [72.0, 21.0, 20.0, 61.0, 20.0, 85.0, 20.0, 25.0, 20.0, 65.0]
# 4.25
# [281.0, 250.0, 358.0, 118.0, 197.0, 71.0, 168.0, 296.0, 198.0, 113.0]
# 5.04225352113