Access attributes in JSON file with python and filter items which attribute matches to specific value

Question

I have JSON file (list.json) as an input:

"Module1": {
  "Description": "",
  "Layer": "1",
  },
  "Vendor": ""
  },
"Module2": {
  "Description": "",
  "Layer": "2",
  },
  "Vendor": ""
  },

"Module3": {
  "Description": "",
  "Layer": "3",
  },
  "Vendor": ""
  },

"Module1": 4
  "Description": "",
  "Layer": "4",
  },
  "Vendor": ""
  },

I am trying to extract all modules (their names) if "Vendor" matches to some criteria, in this case all of the modules with "Vendor": "comp" should be printed (Module2, Module3).

My code is: import json

list_components = []

with open (/list.json) as f:
    swc_list = json.load(f)

for i in swc_list:
   if i['Vendor'] == 'comp':
    list_components.append(i)

print (list_components)

When I run this code, I keep getting: string indices must be integers on line if i['Vendor'] == 'comp':

What would be the best approach to do this?

The best approach is to use debugging techniques to align what the variables actually are with what you think they are. — mkrieger1
– mkrieger1, Commented May 25, 2021 at 15:18
swc_list is not a list. It's a json object. Go through the w3 docs for it. Use pprint for debugging json related things. It will make your life a lot easier — Edo Akse
– Edo Akse, Commented May 25, 2021 at 15:28

zanga · Accepted Answer · 2021-05-27 12:26:59Z

1

You are only missing the fact that your dictionnary of module is a nested one. Each module description is a dictionnary itself.

To iterate through your modules (the keys of your dictionnary) you have to use the .keys() or the .items() method. You can then access every inner dictionnaries.

list_components = []
#iterate through the keys of swc_list
for k in swc_list.keys():
  if swc_list[k]['Vendor'] == 'comp':
    list_components.append(k)

print (list_components)

EDIT:

If you want to take the attributes of your different modules you juste have to access them using their key in the inner dictionary. By specifying which attribute of your dictionary you want you can access its value.

swc_list['Module1'] will give you the entire description dictionnary of the first module

{
        "Description": "",
        "Layer": "1",
        "Vendor": "",
      }

swc_list['Module1']['Layer'] will give you only the value associated with the Layer parameter of th first module

list_components = []

for k in swc_list.keys():
  if swc_list[k]['Vendor'] == 'comp':
    #instead of keeping only the main key (Module) you can append a tuple containing the Module and its attribute Layer 
    list_components.append((k,swc_list[k]['Layer']))

print (list_components)
>>>[('Module2', '1'), ('Module3', '1')]

edited May 27, 2021 at 12:26

answered May 25, 2021 at 15:28

zanga

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2 Comments

John Over a year ago

One more quick question, this will give us "Module2, Module3" as requested, but what if I want also to take their attrib value like "Layer": "1", so at the end I have somehow Module 2 with "Layer": "1", and Module 2 with "Layer": "1"? I can post another question if u like

John Over a year ago

Mate I now have a different situation, I will update question, if you find some time to spend please assist, thanks!

Martin Tovmassian · Accepted Answer · 2021-05-25 15:50:07Z

0

Rather than filtering a list here you need to filter a dictionary since your modules are stored in a JSON object.

You can use Python dictionary comprehension to do this kind of work:

target_modules = dict((key, val) for key, val in json_data.items() if val['Vendor'] == 'comp')

print(target_modules)

answered May 25, 2021 at 15:50

Martin Tovmassian

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