如何使用 Python 从脚本中提取 JSON？

Question

I am parsing a scraped html page that contains a script with JSON inside. This JSON contains all info I am looking for but I can't figure out how to extract a valid JSON.

Minimal example:

my_string = '
        (function(){
          window.__PRELOADED_STATE__ = window.__PRELOADED_STATE__ || [];
          window.__PRELOADED_STATE__.push(
        
           { *placeholder representing valid JSON inside* }
        );
        })()
'

The json inside is valid according to jsonlinter.

The result should be loaded into a dictionary:

import json
import re
my_json = re.findall(r'.*(?={\").*', my_string)[0] // extract json
data = json.loads(my_json)
// print(data)

regex: https://regex101.com/r/r0OYZ0/1

This try results in:

>>> data = json.loads(my_json)
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/code.py", line 90, in runcode
    exec(code, self.locals)
  File "<console>", line 1, in <module>
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/json/__init__.py", line 357, in loads
    return _default_decoder.decode(s)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/json/decoder.py", line 337, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/json/decoder.py", line 355, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 7 (char 6)

How can the JSON be extracted and loaded from the string with Python 3.7.x?

Answer 1

you can try to extract this regex, its a very simple case and might not answerto all possible json variations:

my_string = '''
        (function(){
          window.__PRELOADED_STATE__ = window.__PRELOADED_STATE__ || [];
          window.__PRELOADED_STATE__.push(
        
            {"tst":{"f":3}}
        );
        })()
'''
result = re.findall(r"push\(([{\[].*\:.*[}\]])\)",string3)[0]
result
>>> '{ "tst":{"f":3}}'

to parse it to dictionary now:

import json 

dictionary = json.loads(result)
type(dictionary)
>>>dict

Answer 2

The my_string provided here is not valid JSON. For valid JSON, you can use json.loads(JSON_STRING)

import json

d = json.loads('{"test":2}')
print(d) # Prints the dictionary `{'test': 2}`

Answer 3

Have a look at the below. Note that { *placeholder representing valid JSON inside* } has to be a valid JSON.

my_string = '''
        <script>
            (function(){
              window.__PRELOADED_STATE__ = window.__PRELOADED_STATE__ || [];
              window.__PRELOADED_STATE__.push(
            
               {"foo":["bar1", "bar2"]}
            );
            })()
         </script>
'''

import re, json

my_json = re.findall(r'.*(?={\").*', my_string)[0].strip()
data = json.loads(my_json)
print(data)

Output:

{'foo': ['bar1', 'bar2']}