There are several problems with the logic of your code.

ss = s.read()

reads the entire file s into a single string. The next line

for line in ss:

iterates over each character in that string, one by one. So on each loop line is a single character. In

    line = ss[7:]

you are getting the entire file contents apart from the first 7 characters (in positions 0 through 6, inclusive) and replacing the previous content of line with that. And then

T.append(json.loads(line))

attempts to convert that to JSON and store the resulting object into the T list.

Here's some code that does what you want. We don't need to read the entire file into a string with .read, or into a list of lines with .readlines, we can simply put the file handle into a for loop and that will iterate over the file line by line.

We use a with statement to open the file, so that it will get closed automatically when we exit the with block, or if there's an IO error.

import json

table = []
with open('simple.json', 'r') as f:
    for line in f:
        table.append(json.loads(line[7:]))

for row in table:
    print(row)

output

{'color': '33ef', 'age': '55', 'gender': 'm'}
{'color': '3444', 'age': '56', 'gender': 'f'}
{'color': '3999', 'age': '70', 'gender': 'm'}

We can make this more compact by building the table list in a list comprehension:

import json

with open('simple.json', 'r') as f:
    table = [json.loads(line[7:]) for line in f]

for row in table:
    print(row)

Update: I wrote a solution that does not require reading the entire file in one go. It is too big for a stackoverflow answer, but can be found here jsonstream.

You can use json.JSONDecoder.raw_decode to decode arbitarily big strings of "stacked" JSON (so long as they can fit in memory). raw_decode stops once it has a valid object and returns the last position where was not part of the parsed object. It is poorly documented [1] (see footer), but you can pass this position back to raw_decode and it start parsing again from that position. Unfortunately, the Python json module doesn ot accept strings that have prefixing whitespace. So we need to search to find the first non-whitespace part of your document.

from json import JSONDecoder, JSONDecodeError
import re

NOT_WHITESPACE = re.compile(r'\S')

def decode_stacked(document, idx=0, decoder=JSONDecoder()):
    while True:
        match = NOT_WHITESPACE.search(document, idx)
        if not match:
            return
        idx = match.start()
        
        try:
            obj, idx = decoder.raw_decode(document, idx)
        except JSONDecodeError:
            # do something sensible if there's some error
            raise
        yield obj

s = """

{"a": 1}  


   [
1
,   
2
]


"""

for obj in decode_stacked(s):
    print(obj)

prints:

{'a': 1}
[1, 2]

Note About Missing Documentation

The current signature of raw_decode() dates from 2009, when simplejson was ported into the standard library. The documentation for raw_decode() in simplejson mentions an optional idx argument that can be used to start parsing at an offset. Given that the signature of raw_decode() has not changed since 2009, I think it is fair to assume the API is fairly stable. Especially as decode() uses the idx argument of raw_decode() to ignore prefixing whitespace when parsing a string. And this is exactly what this answer is using the idx argument for too. The documentation of raw_decode() in simplejson is:

raw_decode(s[, idx=0])

Decode a JSON document from s (a str or unicode beginning with a JSON document) starting from the index idx and return a 2-tuple of the Python representation and the index in s where the document ended.

This can be used to decode a JSON document from a string that may have extraneous data at the end, or to decode a string that has a series of JSON objects.

JSONDecodeError will be raised if the given JSON document is not valid.

The content of file you described is not a valid JSON object this is why bot approaches are not working.

To transform in something you can load with json.load(fd) you have to:

1. add a [ at the beginning of the file
2. add a , between each object
3. add a ] at the very end of the file

then you can use the Method 2. For instance:

[ { "a": 1,
    "b" : 2,
    "c" : {
      "d":3
    }
  }, { "e" : 4,
       "f" : 5,
       "g" : {
         "h":6
       }
  }
]

is a valid JSON array

If the file format is exactly as you've described you could do

with open(filename, 'r') as infile:
    data = infile.read()
    new_data = data.replace('}{', '},{')
    json_data = json.loads(f'[{new_data}]')