Python: Handling newlines in json.load() vs json.loads()

Question

According to this answer, newlines in a JSON string should always be escaped. This does not appear to be necessary when I load the JSON with json.load().

I've saved the following string to file:

{'text': 'Hello,\n How are you?'}

Loading the JSON with json.load() does not throw an exception, even though the \n is not escaped:

>>> with open('test.json', 'r') as f:
...   json.load(f)
...
{'text': 'Hello,\n How are you?'}

However, if I use json.loads(), I get an exception:

>>> s
'{"text": "Hello,\n How are you?"}'
>>> json.loads(s)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "c:\Python34\lib\json\__init__.py", line 318, in loads
    return _default_decoder.decode(s)
  File "c:\Python34\lib\json\decoder.py", line 343, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "c:\Python34\lib\json\decoder.py", line 359, in raw_decode
    obj, end = self.scan_once(s, idx)
ValueError: Invalid control character at: line 1 column 17 (char 16)

My questions:

1. Does json.load() automatically escape \n inside the file object?
2. Should one always do \\n regardless of whether the JSON will be read by json.load() or json.loads()?

Answer 1

json.load() reads from a file descriptor and json.loads() reads from a string.

Within your file, the \n is properly encoded as a newline character and does not appear in the string as two characters, but as the correct blank character you know.

But within a string, if you don't double escape the \\n then the loader thinks it is a control character. But newline is not a control sequence for JSON (newline is in fact a character like any other).

By doubling the backslash you actually get a real string with \n in it, and only then will Python transform the \n into a newline char.

Answer 2

EDITED: Already answered here: https://stackoverflow.com/a/16544933/1054458

Maybe the strict option can help:

test.py:

import json

s = '''{
"asdf":"foo
bar"
}'''

print(json.loads(s, strict=False)["asdf"])

output:

$> python test.py
foo
bar