将多个单独的numpy数组写入单个逗号分隔的文本文件

Question

I would like to take multiple numpy arrays and write them to a text file that is comma delimited. Here is the example of my original data and the final data that I am trying to produce:

array([[1., 3., 0., 1.],
       [2., 5., 3., 1.]].....

and so forth. For multiple different arrays of four-column lengths. I can get an out put txt file using write() but I can't get the data into the format shown below:

1., 3., 0., 1.
2., 5., 3., 1.

Also, I need to have the 0th column integers and the 1st through 3rd be floating point.

Cheers.

Answer 1

How about this?

data = array([[1., 3., 0., 1.],
              [2., 5., 3., 1.]].....

with open('output.csv', 'w') as f:
    for x in data:
        f.write('%d,%f,%f,%f\n' % tuple(x))

This outputs

1,3.000000,0.000000,1.000000
2,5.000000,3.000000,1.000000

You can adjust the precision of the floating point output by changing %f to %.2f if you want two decimal places, for instance.

Answer 2

I would recommend using pandas for this:

import numpy
import pandas
data = numpy.array([[1., 3., 0., 1.],
   [2., 5., 3., 1.]])
data = pandas.DataFrame(data,columns=['a','b','c','d'])
data['a'] = data['a'].astype(int)
data.to_csv('outfile.csv')