CODEWITHSUNDEEP
pythonjsonlistloopsdictionary
sergei_22
sergei_22

Reputation: 3

Within a list of dicts, processing all key-value pairs per iteration

Having troubles parsing a list of dictionaries, accessing all key-value pairs per dictionary, through a loop in order to process each k-v at a time.

I have a json file that consists of a list of dictionaries. In simplified form:

[
{"": "0", "a": "3893", "b": "2389", "c": "1209"}, 
{"": "1", "a": "4308", "b": "4560", "c": "9127"},
... 
]

I want to loop through this per dictionary, and for each key-value pair (excluding the first one, assuming it will be skipped because the key is empty) per iteration, having access to the a,b,c k-v pairs of one dict, so that they are individually processed.

I tried:

import json

with open("file.json", "r") as read_file:
    data = json.load(read_file)

    result_list = []
    for d in data:
        result_list.append([v for k,v in d.items()])

    for k, v in enumerate(result_list.items()): 
        # process each key-value pair

But I get the following error:

Traceback (most recent call last):
  File "somescript.py", line 28, in <module>
    for k, v in enumerate(result_list.items()): 
AttributeError: 'list' object has no attribute 'items'

Meanwhile I tried:

import json

with open("file.json", "r") as read_file:
data = json.load(read_file)

for i in data:
    print(i, data[i])

And get: 

  Traceback (most recent call last):
  File "somescript.py", line 26, in <module>
    print(i, dat[i])
TypeError: list indices must be integers or slices, not dict

The code is faulty, I don't yet know how to achieve the above, it may be simple but I haven't found it yet.

Upvotes: 0

Views: 83

Answers (3)

Jab
Jab

Reputation: 27515

You should be able to load the entire list without rebuilding it just using json.load, then iterate over it and the dicts 

import json

with open("file.json", "r") as read_file:
    data = json.load(read_file)

for d in data:
    for i, (k, v) in enumerate(d.items()):
        print(i, k, v)

That said I suggest you save the file as a normal JSON file as it seems the first key/value in each dict is supposed to be an ID field so it should look as follows:

{  
    "0": {
        "a":"3893",
        "b":"2389",
        "c":"1209"
    },
    "1": {
        "a":"4308",
        "b":"4560",
        "c":"9127"
    }
}

Which you can do using a dict comprehension:

with open("file.json", 'w') as out_file:
    json.dump({d.pop(""): d for d in data}, out_file, indent=4)

Then all you'd need to do is simply iterate over the dicts:

with open("file.json", "r") as read_file:
    data = json.load(read_file)

    for _id, item in data.items():
        for k, v in item.items():
            print(_id, k, v)

Upvotes: 0

Code-Apprentice
Code-Apprentice

Reputation: 83557

    result_list = []
    for d in data:
        result_list.append([v for k,v in d.items()])

This creates a list of lists. Note that when you do this, you are throwing away the keys in your dictionaries. This probably isn't what you want.

    for k, v in enumerate(result_list.items()): 
        # process each key-value pair

You get an error here because result_list is a list, not a dictionary. Lists do not have a method named items().

I suggest instead that you iterate over data directly. There is no need for result_list:

for d in data:
    for k, v in d.items():
        # process each key-value pair

Upvotes: 0

jhelphenstine
jhelphenstine

Reputation: 423

The first part of your problem is in your enumerate call:

    for k, v in enumerate(result_list): # take off the .items())
        # process each key-value pair

You don't invoke .items() on the result_list; enumerate consumes it as a list.

Answering the second of your problems:

import json

with open("file.json", "r") as read_file:
data = json.load(read_file)

for i in data:
    print(i, data[i])

Assuming that json is a list of dictionaries like you've been using, you'll need to:

for item in data:
    for key in item:
        print(key, item[key])

to account for double-dereferencing.

Upvotes: 1

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