How to write the values of a dictionary into a CSV file

Question

This is my Python version:

import sys

print(sys.version)

>> 3.6.9 (default, Nov  7 2019, 10:44:02) 
>> [GCC 8.3.0]

And I'm running on a Google Colaboratory notebook.

I'm newbie with Python and I haven't found any useful example to show me how to write the following dictionary to a CSV.

print(my_dict)

>> {'loss': [0.411, 0.115, 0.147, 0.078, 0.032], 'accuracy': [0.996, 0.997, 0.997, 0.997, 0.997], 'val_loss':  [0.147, 0.100, 0.187, 0.065, 0.052], 'val_accuracy': [0.99, 0.99, 0.99, 0.996, 0.996]}

And:

print(type(my_dict))

>> <class 'dict'>

And I want to get this CSV file:

loss,accuracy,val_loss,val_accuracy
0.411,0.996,0.147,0.99
0.115,0.997,0.100,0.99
0.147,0.997,0.187,0.99
0.078,0.997,0.065,0.996
0.032,0.997,0.052,0.996

The values for each key as columns.

I'm trying with this code (I'm using stdout to see what it is happening):

import sys
import csv

w = csv.DictWriter(sys.stdout, my_dict.keys())
w.writeheader()
w.writerows(my_dict.values())

But I get the error:

AttributeError: 'list' object has no attribute 'keys'

I have changed the last line with this:

w.writerows(my_dict)

And I get the same error:

AttributeError: 'str' object has no attribute 'keys'

And with this:

w.writerows(results.history.items())

With the error:

AttributeError: 'tuple' object has no attribute 'keys'

And also, I have tried:

for key, value in my_dict.items():
  w.writerow([key,value])

With the error:

AttributeError: 'list' object has no attribute 'keys'

Another test:

for data in my_dict:
  w.writerow(data)

With the error:

AttributeError: 'str' object has no attribute 'keys'

How can I do it?

@HarshalParekh I have updated my question with the CSV file format. — VansFannel
– VansFannel, Commented Feb 27, 2020 at 18:23

Harshal Parekh · Accepted Answer · 2020-02-27 18:44:57Z

2

import csv

my_dict = {'loss': [0.411, 0.115, 0.147, 0.078, 0.032], 'accuracy': [0.996, 0.997, 0.997, 0.997, 0.997], 'val_loss':  [0.147, 0.100, 0.187, 0.065, 0.052], 'val_accuracy': [0.99, 0.99, 0.99, 0.996, 0.996]}

with open("test.csv", "w") as outfile:
  writer = csv.writer(outfile)
  writer.writerow(my_dict.keys())
  writer.writerows(zip(*my_dict.values()))

Output:

loss,accuracy,val_loss,val_accuracy
0.411,0.996,0.147,0.99
0.115,0.997,0.1,0.99
0.147,0.997,0.187,0.99
0.078,0.997,0.065,0.996
0.032,0.997,0.052,0.996

If you need the dictionary sorted:

keys = sorted(my_dict.keys())
with open("test.csv", "w") as outfile:
   writer = csv.writer(outfile, delimiter = ",")
   writer.writerow(keys)
   writer.writerows(zip(*[my_dict[key] for key in keys]))

Sorted Output:

accuracy,loss,val_accuracy,val_loss
0.996,0.411,0.99,0.147
0.997,0.115,0.99,0.1
0.997,0.147,0.99,0.187
0.997,0.078,0.996,0.065
0.997,0.032,0.996,0.052

3 Comments

VansFannel Over a year ago

What do you mean with "If you don't care about the order"? Thanks.

Harshal Parekh Over a year ago

I assumed my_dict.keys() would reorder, but it didn't. Just in case you need the output sorted, I will add another snippet.

VansFannel Over a year ago

Thanks a lot for your help.

jjramsey · Accepted Answer · 2020-02-27 18:57:42Z

The reason you are getting all those AttributeError exceptions is that you aren't using the DictWriter version of writerow() correctly. That version of writerow takes a dictionary as an argument, where the keys of the dictionary are the names of the row fields, and the values of the dictionary are the row field values. That means that row i of your CSV file (not counting the header), should be written something like this:

w.writerow({'loss': my_dict['loss'][i],
            'accuracy': my_dict['accuracy'][i],
            'val_loss': my_dict['val_loss'][i],
            'val_accuracy': my_dict['val_accuracy'][i]})

Since this is kind of clumsy, Harshal Parekh's approach to writing the CSV file is better, though his first approach does rely on Python ordering its dictionary entries a certain way. (Older versions of Python would need to to have my_dict to be of type OrderedDict for that first approach to work.)

Collectives™ on Stack Overflow

How to write the values of a dictionary into a CSV file

2 Answers 2

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related