reading file into numpy array python

Question

For an assignment i need to read a file and write into a numpy array, the data consists of a sting and 2 floats:

# naam  massa(kg)   radius(km)
Venus   4.8685e24   6051.8
Aarde   5.9736e24   6378.1
Mars    6.4185e23   3396.2
Maan    7.349e22    1738.1
Saturnus    5.6846e26   60268

the following was my solution to this problem:

def dataread(filename):
temp = np.empty((1,3), dtype=np.object)
x = 0
f = open(filename,'r')
for line in f:
    if line[0] !='#' :
        l = line.split('\t')
        temp[0,0], temp[0,1] , temp[0,2] = l[0] , float(l[1]) , float(l[2])
        if x == 0:
            data = temp
        if x > 0:
            data = np.vstack((data,temp))
        x+=1
f.close()   
return data

somehow this returns the following array:

[['Aarde' 5.9736e+24 6378.1]
['Aarde' 5.9736e+24 6378.1]
['Mars' 6.4185e+23 3396.2]
['Maan' 7.349e+22 1738.1]
['Saturnus' 5.6846e+26 60268.0]]

The first line is being read but does not end up in the array while the second row is read in twice. What am I doing wrong ? I'm new to python so any comments on efficiency are also very much appreciated

Thanks in advance

Answer 1

This will read in your three columns into a numpy structured array:

import numpy as np
data = np.genfromtxt(
    'data.txt',
     dtypes=None,  # determine types automatically
     names=['name', 'mass', 'radius'],
)
print(data['name'])