CODEWITHSUNDEEP
python
user2
user2

Reputation: 31

how to read a json array from specific line of a file with python without using eval function

i have a file which has that json array

[
  {'sector':'1','info':[{'id':'1234','pos':'55039974','risk':'low'},{'id':'3333','pos':'44530354','risk':'middle'}]},
  {'sector':'2','info':[{'id':'2434','pos':'45455554','risk':'high'},{'id':'4444','pos':'4454555','risk':'high'}]}
]

as a single line

[{'sector':'1','info':[{'id':'1234','pos':'55039974','risk':'low'},{'id':'3333','pos':'44530354','risk':'middle'}]},{'sector':'2','info':[{'id':'2434','pos':'45455554','risk':'high'},{'id':'4444','pos':'4454555','risk':'high'}]}]

in a file as line 2. how can i read just line 2 which is that json array out of that file and print it with

print(str(lines[0]['sector'][0]['id']))

? i dont want to use eval function, because if i use a huge array like 1E6 entries eval increase my RAM up to 6Gb. Thats the reason why i try to figure out how it would works with other functions to read a string and convert it to an array. thx for any help

Update: i tried:

with open('file.txt') as f:
  """ 
  v1: 
  t = f.readlines()[2]
  s = json.loads(t)
  print(s[0]['sector'])
  v1 output: 
  Traceback (most recent call last): s = json.loads(t)
    File "/usr/lib/python3.7/json/__init__.py", line 348, in loads
     return _default_decoder.decode(s)
     ...
    ...
  json.decoder.JSONDecodeError: Expecting property name enclosed in double quotes: line 1 column 3 (char 2)

  v2:
  t = f.readlines()[2]
  x = json.dumps(t, indent=4)
  #x = json.dumps(t)
  s = json.loads(x)
  print(s[0]['sector'])
  v2 output:
  TypeError: string indices must be integers

  v3:
  t = f.readlines()[2]
  x = json.dumps(t, indent=4)
  s = json.JSONDecoder().decode(json.JSONEncoder().encode(x))
  #s = json.JSONDecoder().decode(x)
  #s = json.JSONEncoder().encode(x)
  print(s[0]['sector'])
  v3 output:
  TypeError: string indices must be integers
  """

Update 2 The array is the problem! this constalation without [ and sector 2 works

{"sector":"1","info":[{"id":"1234","pos":"55039974","risk":"low"},{"id":"RS11591147x","pos":"44530354","risk":"middle"}]}

Update 3 - (closed) the array is ok, but i had to replace the ' to " in each array. and the memory just increase from 450Mb up to 700Mb. thats a huge to 6Gb. the problem is that the txt files increase vom 30Mb to 50Mb but who cares? xD

whereIsMyArray = 1
with open('file.txt', 'r') as fp:
  line = fp.readlines()[whereIsMyArray].replace("'", '"')
  data = json.loads(line)
print(data[1]['info'][1]["risk"])

Upvotes: 0

Views: 2791

Answers (1)

IoaTzimas
IoaTzimas

Reputation: 10624

You could try with json library function json.loads:

import json

with open('yourfile.txt') as f:
    s=f.readlines()[1]

result=json.loads(s)

Upvotes: 1

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