How to import CSV file as NumPy array?

Question

Say I have a CSV file.csv in this format:

dfaefew,432,1
vzcxvvz,300,1
ewrwefd,432,0

How to import the second column as a NumPy array and the third column as another one like this:

second = np.array([432, 300, 432])
third = np.array([1, 1, 0])

Asked By: user3692521

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Source

Answer 1

You can use numpy.loadtxt:

In [15]: !cat data.csv
dfaefew,432,1
vzcxvvz,300,1
ewrwefd,432,0

In [16]: second, third = loadtxt('data.csv', delimiter=',', usecols=(1,2), unpack=True, dtype=int)

In [17]: second
Out[17]: array([432, 300, 432])

In [18]: third
Out[18]: array([1, 1, 0])

Or numpy.genfromtxt

In [19]: second, third = genfromtxt('data.csv', delimiter=',', usecols=(1,2), unpack=True, dtype=None)

The only change in the arguments is that I used dtype=None, which tells genfromtxt to infer the data type from the values that it finds in the file.

Answered By: Warren Weckesser

Answer 2

numpy.genfromtxt() is the best thing to use here

import numpy as np
csv = np.genfromtxt ('file.csv', delimiter=",")
second = csv[:,1]
third = csv[:,2]

>>> second
Out[1]: array([ 432.,  300.,  432.])

>>> third
Out[2]: array([ 1.,  1.,  0.])

Answered By: Anoop

How to import CSV file as NumPy array?

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