Python: How to write to csv a dict of list “in line”?

Question

I wish to write my dict of list to a csv file, I need to sort my row by key name:

import csv

dict_of_list = {"key1": [1,2,3], "key2": [4,5,6], "key3": [7,8,9]}

#line bugged corrected bellow:
# keys = sorted(dict_of_list.keys())
writer.writerows(sorted([k, *vs] for k, vs in dict_of_list.items()))


with open("P:/Code/Python/CSV/dict_of_list.csv", "w") as tmp:
    writer = csv.writer(tmp)
    writer.writerows(zip(dict_of_list.items()))

I need the csv file to be ordered like:

key1, 1, 2, 3
key2, 4, 5, 6
key3, 7, 8, 9

Actualy my output csv is:

"('key1', [1, 2, 3])"
"('key2', [4, 5, 6])"
"('key3', [7, 8, 9])"

I've tried other code but I could only put the keys in the header or no keys at all.

I would be grateful if someone could give me a push.

Answer 1

The problem is you are writing the tuples, do this instead:

import csv

dict_of_list = {"key2": [4, 5, 6], "key3": [7, 8, 9], "key1": [1, 2, 3], }

with open("output.csv", "w") as tmp:
    writer = csv.writer(tmp)
    writer.writerows([k, *vs] for k, vs in sorted(dict_of_list.items()))

Output

key1,1,2,3
key2,4,5,6
key3,7,8,9

The expression:

[k, *vs] for k, vs in dict_of_list.items()

creates a list where the first element is the key and the rest of the elements are the values. Update The *vs unpacks the elements of the list, see here . If you want the elements sorted by key, do this, as suggested by @tdelaney:

writer.writerows(sorted([k, *vs] for k, vs in dict_of_list.items()))

Answer 2

Instead of managing the writing of the file all by yourself you could use the pandas library instead.

For that you simply create a pandas DataFrame (like a table) from your dictionary with the orientation set to orient=index , because your dictionary keys should serve as the rows of your table. Then you simply use the DataFrame method to_csv to write your csv file. You can use the header=False parameter when you do not want a header.

import pandas as pd
df = pd.DataFrame.from_dict(dict_of_list, orient="index").sort_index()
df.to_csv("test.csv", sep=";", header=False)

Answer 3

The problem can also be solved using pandas's method to_csv()

import pandas
dict_of_list = {"key1": [1,2,3], "key2": [4,5,6], "key3": [7,8,9]}

df = pandas.DataFrame(dict_of_list)
df.T.sort_index().to_csv("test.csv",sep=";",header=False)