How to select dictionary by using certain keys in Python?

Question

I have this kind of JSON data and have around 100 questions. How can I filter the question only up to 40?

This is the sample of data:

data=[{"id": "AA11",
"resp": [
    {"answer": "A","number": 1},
    {"answer": "A","number": 2},
    {"answer": "B","number": 3},
    {"answer": "D","number": 4},
    {"answer": "E","number": 5}
]},
{"id": "AA22",
"resp": [
    {"answer": "A","number": 1},
    {"answer": "A","number": 2},
    {"answer": "B","number": 3},
    {"answer": "D","number": 4},
    {"answer": "E","number": 5}
]},
{"id": "AA33",
"resp": [
    {"answer": "A","number": 1},
    {"answer": "A","number": 2},
    {"answer": "B","number": 3},
    {"answer": "D","number": 4},
    {"answer": "E","number": 5}
]}]

Can I extract the data only up to number 3 as example in this case?

Output:

data=[{"id": "AA11",
"resp": [
    {"answer": "A","number": 1},
    {"answer": "A","number": 2},
    {"answer": "B","number": 3}
]},
{"id": "AA22",
"resp": [
    {"answer": "A","number": 1},
    {"answer": "A","number": 2},
    {"answer": "B","number": 3}
]},
{"id": "AA33",
"resp": [
    {"answer": "A","number": 1},
    {"answer": "A","number": 2},
    {"answer": "B","number": 3}
]}]

Does this answer your question? How to take the first N items from a generator or list in Python? — Masklinn
– Masklinn, Commented Apr 2, 2020 at 7:04

Alexander Lekontsev · Accepted Answer · 2020-04-02 07:04:15Z

2

for item in data:
    item['resp'] = item['resp'][:3]

answered Apr 2, 2020 at 7:04

Alexander Lekontsev

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Comments

Serge Ballesta · Accepted Answer · 2020-04-02 07:14:23Z

2

The Pythonic way would be a comprehension:

filtered = [{'id': d['id'], 'resp': [x for x in d['resp'] if x['number'] <= 3]}
            for d in data]

It gives as expected:

[{'id': 'AA11',
  'resp': [{'answer': 'A', 'number': 1},
           {'answer': 'A', 'number': 2},
           {'answer': 'B', 'number': 3}]},
 {'id': 'AA22',
  'resp': [{'answer': 'A', 'number': 1},
           {'answer': 'A', 'number': 2},
           {'answer': 'B', 'number': 3}]},
 {'id': 'AA33',
  'resp': [{'answer': 'A', 'number': 1},
           {'answer': 'A', 'number': 2},
           {'answer': 'B', 'number': 3}]}]

answered Apr 2, 2020 at 7:14

Serge Ballesta

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1 Comment

Shane Abram Mendez Over a year ago

"...Complex is better than complicated. Flat is better than nested. Sparse is better than dense. Readability counts..." -The Zen of Python

Shane Abram Mendez · Accepted Answer · 2020-04-02 07:17:24Z

1

Filtering up to a specific element should can be done like this

def filter(question,num):
    temp = {}
    for key in question:
        temp[key] = question[key]
    temp['resp'] = question['resp'][:num]
    return temp

def filter_list(questions,num):
    temp = []
    for question in questions:
        temp.append(filter(question,num))
    return temp

data = [{}...]
filtered_data = filter_list(data)

You'll notice that filter creates a copy of question and only changes the copy. It can be useful to change data structures, but it's good practice to treat data structures as immutable where possible.

As a bonus, you won't lose any of the original data this way

answered Apr 2, 2020 at 7:17

Shane Abram Mendez

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Comments

Prashant Kumar · Accepted Answer · 2020-04-02 07:21:23Z

1

Try this :

new_data = data[0:40]
for item in new_data:
    item['resp'] = item['resp'][0:3]

This solution will create a new dictionary with expected values.

edited Apr 2, 2020 at 7:21

answered Apr 2, 2020 at 7:09

Prashant Kumar

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