python - TypeError in for loop -

i'm having trouble code, have text file 633,986 tuples, each 3 values (example: first line -0.70,0.34,1.05). want create array take magnitude of 3 values in tuple, elements a,b,c, want magnitude = sqrt(a^2 + b^2 + c^2).

however, i'm getting error in code. advice?

import math fname = '\\pathname\\gerrystenhz.txt' open(fname, 'r')  magn1 = []; in range(0, 633986):     magn1[i] = math.sqrt((fname[i,0])^2 + (fname[i,1])^2 + (fname[i,2])^2)  typeerror: string indices must integers, not tuple 

you need use lines of file , csv module (as martijn pieters points out) examine each value. can done list comprehension , with:

with open(fname) f:         reader = csv.reader(f)         magn1 = [math.sqrt(sum(float(i)**2 in row)) row in reader] 

just make sure import csv well

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to explain issues having (there quite few) i'll walk through more drawn out way this.

you need use openreturns. open takes string , returns file object.

f = open(fname) 

i'm assuming range in loop suppose number of lines in file. can instead iterate on each line of file 1 one

for line in f: 

then numbers on each line, use str.split method of split line on commas

    x, y, z = line.split(',') 

convert 3 floats can math them

    x, y, z = float(x), float(y), float(z) 

then use ** operator raise power, , take sqrt of sum of 3 numbers.

    n = math.sqrt(x**2 + y**2 + z**2) 

finally use append method add of list

    magn1.append(n)