Values in List of Dicts - Python 3

Question

I want to extract a list of dictionary values so I can write them to csv.

Using the info in this previous SO question I am attempting to replicate for all key, values.

In [41]: dicts = [
    ...: {"name": "Tom", "age": 10},
    ...: {"name": "Mark", "age": 5},
    ...: {"name": "Pam", "age": 7},
    ...: {"name": "Dick", "age": 12},
    ...: ]

However the output I am getting is very mixed, sometimes its a dict and sometimes a value.

In [25]: for item in dicts:
    ...:     for k, v in item.items():
    ...:         print("Key: {0} and Value: {1}".format(k,v))
    ...:
    ...:
Key: name and Value: {'name': 'Dick', 'age': 12, 0: {...}}
Key: age and Value: 10
Key: 0 and Value: {'name': 'Dick', 'age': 12, 0: {...}}
Key: name and Value: Mark
Key: age and Value: 5
Key: name and Value: Pam
Key: age and Value: 7
Key: name and Value: Dick
Key: age and Value: 12
Key: 0 and Value: {'name': 'Dick', 'age': 12, 0: {...}}

I want the output to have no dicts in it all keys and values extracted. There are better ways to do this I see but error was from pasting into ipython incorrectly.

Edited Updated Dicts Updated Output with updated Dicts does work as expected.

In [49]: for item in dicts:
    ...:     for k, v in item.items():
    ...:         print("Key: {0} and Value: {1}".format(k,v))
    ...:
Key: name and Value: Tom
Key: age and Value: 10
Key: name and Value: Mark
Key: age and Value: 5
Key: name and Value: Pam
Key: age and Value: 7
Key: name and Value: Dick
Key: age and Value: 12

Cannot reproduce. I'm getting what you should, or rather, what you should expect. — juanpa.arrivillaga, Aug 30 '17 at 22:36
Yeah, `print(dicts)` should show you the issue. Note, you've definied `dicts` on input `1`, but you are showing the output `25`, so *something* is happening in-between. Also, I'm pretty sure what you pasted in `1` should throw a syntax-error... — juanpa.arrivillaga, Aug 30 '17 at 22:39
Also, note the presence of the recursive `0: {...}`, which suggests you've done something like: `dicts[0][0] = dicts[0]` followed by something like `dicts[3][0] = dicts[0]` — juanpa.arrivillaga, Aug 30 '17 at 22:42

Rudrani Angira · Answer 1 · 2017-08-30T23:10:59.030

1

Why not just enumerate on the list and extract the values:

for i, entry in enumerate(dicts):
...             print entry['name']," ",entry['age']

And then the values can be written to the csv file

with open('dict.csv', 'wb') as csv_file:
...         writer = csv.writer(csv_file)
...         for i, entry in enumerate(dicts):
...             writer.writerow([entry['name'],entry['age']])

edited Aug 30 '17 at 23:10

answered Aug 30 '17 at 22:58

Rudrani Angira

956
2
14
28

1

Because I use python3 your eumerate is good but I got it working using for i, entry in enumerate(dicts): print("{0}, {1}".format(entry['name'], entry['age'])) – sayth Aug 30 '17 at 23:19

score 1 · Answer 2 · answered Aug 30 '17 at 23:38

You can re-construct the dict to meet your needs:

dicts = [{'key': k, 'value': v} for item in dicts for k,v in item.items()]

for item in dicts:
    print("Key: {key} and Value: {value}".format(**item))

But, to write them directly to csv, there is a better way:

import csv

dicts = [{'key': k, 'value': v} for item in dicts for k,v in item.items()]

with open('dicts.csv', 'wb') as f:
    dict_writer = csv.DictWriter(f, dicts[0].keys())
    dict_writer.writeheader()
    dict_writer.writerows(dicts)

Doctor Core · Answer 3 · 2018-04-04T06:15:39.247

0

You can convert a list of same-keys dicts into a dict with the same keys and values are lists of the original values in original order:

dicts = [
    {"name": "Tom", "age": 10},
    {"name": "Pam", "age": 7},
    {"name": "Dick", "age": 12},
]

dictoflists = {k: [d[k] for d in dicts] for k in dicts[0].keys()}

edited Apr 04 '18 at 06:15

answered Apr 04 '18 at 06:09

Doctor Core

102
5

Values in List of Dicts - Python 3

3 Answers3