二维NumPy数组的切片截面

Question

I'm looking to print a cross-section of a numpy array. I am looking to pull the first 15 rows and only data from the 5th index column.

import csv as csv
import numpy as np 

csv_file_object = open('train.csv', 'rU')
header = next(csv_file_object)
data = []

for row in csv_file_object:
    data.append(row)

data = np.array(data)

print(data[0:15,5])

When I run the above code, I receive the following error: IndexError: too many indices for array.

Running the code without adding the column filter works as expected. The csv file is a 12x892 (x,y) dataset.

Answer 1

The csv_file_object is a file object contains all lines of your csv file without splitting. You have to use csv module to read them properly:

with open('train.csv', 'rU') as csv_file_object:
    reader = csv.DictReader(csv_file_object)
    data = np.array([row.values() for row in reader])

But since you want to convert them to a numpy array you better to use genfromtxt function:

data = np.genfromtxt('train.csv')

You can pass arguments like dtype , delimiter and names (a boolean for keeping the headers).

Answer 2

UPDATE: I did not call csv.reader() prior to opening the file

import csv as csv
import numpy as np 

csv_file_object = csv.reader(open('train.csv', 'rU'))
header = next(csv_file_object)
data = []

for row in csv_file_object:
    data.append(row)

data = np.array(data)

print(data.shape)
print(data[0:15,5])