normalize a column in pandas dataframe

Question

I am able to import data from json file using this code...

import requests
from pandas.io.json import json_normalize

url = "https://datameetgeobk.s3.amazonaws.com/image_list.json"

resp = requests.get(url=url)
df = json_normalize(resp.json()['Images'])
df.head()

But the column "BlockDeviceMappings" is actually a list and each item has DeviceName and Ebs parameters those are string and dicts. How do I further normalize my dataframe to include all the details in separate columns?

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My screenshot does not match with the one shown in the answer. The Ebs column (second from left) is a dictionary.

Answer 1

import requests
import pandas as pd

url = "https://datameetgeobk.s3.amazonaws.com/image_list.json"

resp = requests.get(url=url)
resp = resp.json()

What you have so far:

df = pd.json_normalize(resp['Images'])

BlockDeviceMappings cast to all columns

inner_keys = [x for x in resp['Images'][0].keys() if x != 'BlockDeviceMappings']

df_bdm = pd.json_normalize(resp['Images'], record_path=['BlockDeviceMappings'], meta=inner_keys, errors='ignore')

Separate bdm_df:

bdm_df = pd.json_normalize(resp['Images'], record_path=['BlockDeviceMappings'])

You will no doubt wonder why df has 39995 entries, while bdm_df has 131691 entries. This is because BlockDeviceMappings is a list of dicts of varying lengths:

bdm_len = [len(x) for x in df.BlockDeviceMappings]
max(bdm_len)
>>> 31

Sample BlockDeviceMappings entry:

[{'DeviceName': '/dev/sda1',
  'Ebs': {'DeleteOnTermination': True,
   'SnapshotId': 'snap-0aac2591b85fe677e',
   'VolumeSize': 80,
   'VolumeType': 'gp2',
   'Encrypted': False}},
 {'DeviceName': 'xvdb',
  'Ebs': {'DeleteOnTermination': True,
   'SnapshotId': 'snap-0bd8d7828225924a7',
   'VolumeSize': 80,
   'VolumeType': 'gp2',
   'Encrypted': False}}]

df_bdm.head()