How to output numpy list into cvs file python 3.6

Question

I have a python list as follows:

[(numpy.datetime64('2000-04-01'), 'pie'),
 (numpy.datetime64('2000-04-01'), 'apple'),
 (numpy.datetime64('2000-04-01'), 'orange'),
 (numpy.datetime64('2000-04-01'), 'mango'),
 (numpy.datetime64('2000-04-01'), 'pears')]

i want it to a csv file output as following

|    date    |  item |
+------------+-------+
| 2000-04-01 | pie   |
| 2000-04-01 | apple |
|     ...    |  ...  |

This is not a numpy object, numpy doesn't have lists. You can turn your list into a pandas' dataFrame and then save it with to_csv method. — anishtain4
– anishtain4, Commented Jun 4, 2018 at 19:13
Iterate on the list, format each element as you wish and write to the file. Just ordinary python text file creation. — hpaulj
– hpaulj, Commented Jun 4, 2018 at 20:18

as - if · Accepted Answer · 2018-06-04 20:47:03Z

1

I was able to output as csv file finally.

import csv
with open('date_prop.csv','w',newline='') as out:
    csv_out=csv.writer(out)
    csv_out.writerow(['date','item'])
    for row in f2:
        csv_out.writerow(row)

answered Jun 4, 2018 at 20:47

as - if

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Comments

hpaulj · Accepted Answer · 2018-06-05 03:51:07Z

Straight forward Python file write:

In [116]: with open('test','w') as f:
     ...:     print('   date   item', file=f)
     ...:     for t in alist:
     ...:         print('%s   %s'%t, file=f)
     ...:         
In [117]: cat test
   date   item
2000-04-01   pie
2000-04-01   apple
2000-04-01   orange
2000-04-01   mango
2000-04-01   pears

The key is that str(np.datetime64('2000-04-01') is formatted as you want.

And object dtype array can be written with savetxt with the right fmt:

In [121]: arr = np.array(alist)
In [122]: arr
Out[122]: 
array([[numpy.datetime64('2000-04-01'), 'pie'],
       [numpy.datetime64('2000-04-01'), 'apple'],
       [numpy.datetime64('2000-04-01'), 'orange'],
       [numpy.datetime64('2000-04-01'), 'mango'],
       [numpy.datetime64('2000-04-01'), 'pears']], dtype=object)
In [123]: np.savetxt('test', arr, fmt='%s', delimiter=',', header='date item')
In [124]: cat test
# date item
2000-04-01,pie
2000-04-01,apple
2000-04-01,orange
2000-04-01,mango
2000-04-01,pears

I could also create a structured array and write that with savetxt

In [125]: arr = np.array(alist, dtype='datetime64[D], U10')
In [126]: arr
Out[126]: 
array([('2000-04-01', 'pie'), ('2000-04-01', 'apple'),
       ('2000-04-01', 'orange'), ('2000-04-01', 'mango'),
       ('2000-04-01', 'pears')], dtype=[('f0', '<M8[D]'), ('f1', '<U10')])
In [127]: np.savetxt('test', arr, fmt='%s', delimiter=',  ', header='date   item
     ...: ')
In [128]: cat test
# date   item
2000-04-01,  pie
2000-04-01,  apple
2000-04-01,  orange
2000-04-01,  mango
2000-04-01,  pears

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