Create different arrays from csv file using python

Question

I want to create 6 arrays (one for each column) from my csv which looks like below:

The first column is the point name(Pt_name) and it contains strings. All the other are containing float numbers (Hz_angle, Vz_angle, Slope_Dist, Reference_Ht, Instrument_Height)

The purpose is to be able to perform mathematical operations between the elements of the float columns.

Any ideas?

S2,0.000000,98.799682,12.056200,1.700000,1.545000
1,0.000052,98.799806,12.056800,1.700000,1.545000
2,78.734236,99.822405,17.919000,0.000000,1.545000
3,78.861726,108.352791,17.213700,0.000000,1.545000
4,28.505234,91.249749,6.779200,0.000000,1.545000
5,34.011213,110.976488,6.840100,0.000000,1.545000
6,27.427827,106.134477,6.387900,0.000000,1.545000
48,0.926245,98.540506,25.413900,0.000000,1.545000
49,389.808941,99.812394,25.351000,0.000000,1.545000
S1,122.545107,99.563594,12.056300,1.700000,1.545000
50,200.000125,99.563463,12.058800,1.700000,1.545000
51,60.723043,95.842462,8.607300,0.000000,1.545000

Asked By: Mou Xaxa

||

Source

Answer 1

Didn’t test it, but something like this should work:

import csv

Pt_names = []
Hz_angles = []
Vz_angles = []
Slope_Dists = []
Reference_Hts = []
Instrument_Heights = []
with open(csv_file, 'r') as fh:
    reader = csv.reader(fh)
    for row in reader:
        Pt_name = row[0]
        # list comprehension for float conversion
        Hz_angle, Vz_angle, Slope_Dist, Reference_Ht, Instrument_Height = [float(value) for value in row[1:]]
        Pt_names.append(Pt_name)
        Hz_angles.append(Hz_angle)
        Vz_angles.append(Vz_angle)
        Slope_Dists.append(Slope_Dist)
        Reference_Hts.append(Reference_Ht)
        Instrument_Heights.append(Instrument_Height)

Answered By: martyn

Answer 2

If you want to do math with arrays, you should look into numpy. To load your data, you can do:

In [1]: import numpy as np

In [2]: numbers = ['Hz_angle', 'Vz_angle', 'Slope_Dist', 'Reference_Ht', 'Instrument_Height']

In [3]: dt = np.dtype([('Pt_name', np.bytes_, 5)] + [(name, np.float32) for name in numbers])

In [4]: data = np.loadtxt('/tmp/csv', delimiter=',', dtype=dt)

In [5]: data['Vz_angle']
Out[5]: 
array([  98.79968262,   98.79980469,   99.82240295,  108.35279083,
         91.24974823,  110.97648621,  106.13447571,   98.54050446,
         99.81239319,   99.563591  ,   99.5634613 ,   95.84246063], dtype=float32)

This reads the file into an array of records of type dt.

Answered By: Lev Levitsky

Create different arrays from csv file using python

Question:

Answers: