Loop through JSON file python

Question

In JSON data file, I'd like to obtain the first elements in the object list. So, John, Sam, and James in this case.

I can get first element like this below, but how do I loop through the first objects in that list without specifically replacing below values like 0,1,2?

data[0]["name"][0]
data[1]["name"][0]
data[2]["name"][0]
data[3]["name"][0]
...

code

with open('data.json') as f:
    data = json.load(f)
##prints list
print data[0]["name"]
##print first element in that list
print data[0]["name"][0]

json

[{
       "name":[ "John", "Sam", "Rick"]
   },
   {
       "name":[ "Sam", "Paul", "Like"]
   },
{
       "name":[ "James", "Saul", "Jack"]
   }
]

What did you try so far? If you have not googled "for loop in python" so far, I strongly recommend you to do so. — Niklas Mertsch
– Niklas Mertsch, Commented Apr 1, 2019 at 17:43

Inon Peled · Accepted Answer · 2019-04-01 17:44:33Z

3

def get_first_name_from_each_dict(data_list):
    return [d['name'][0] for d in data]

print(get_first_name_from_each_dict([
    {
        "name": ["John", "Sam", "Rick"]
    },
    {
        "name": ["Sam", "Paul", "Like"]
    },
    {
        "name": ["James", "Saul", "Jack"]
    }
]))

['John', 'Sam', 'James']

answered Apr 1, 2019 at 17:44

Inon Peled

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1 Comment

Inon Peled Over a year ago

By the way, if you wish to obtain unique names that appear first in each list, change the output list to a set.

Cup of Java · Accepted Answer · 2019-04-01 17:45:16Z

1

You should look into the types of loops in Python to fully understand what this code is doing

You can use a for loop to iterate through every object in the data list

names = []
for name_list in data:
    names.append(name_list["name"][0])

Or you can do it all in one line with list comprehension

names = [name_list["name"][0] for name_list in data]

answered Apr 1, 2019 at 17:45

Cup of Java

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Comments

Aaron_ab · Accepted Answer · 2019-04-01 17:50:58Z

1

names_res = map(lambda i: i['name'][0], data)

It outputs a lazy 'generator' which is memory efficient, which is much better than consuming all data

print(list(names_res))

>> ['John', 'Sam', 'James']

edited Apr 1, 2019 at 17:50

answered Apr 1, 2019 at 17:44

Aaron_ab

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