Parsing JSON using Pandas - issue with additional \ escape characters

Question

I'm downloading files from S3 that contains JSON (like) data which I intend to parse into a Pandas dataframe using pd.read_json .

My problem is that the files dumped into the S3 bucket use an 'octal escape' formatting for non english characters but Python/Pandas objects to the fact that an escape for the \\ character is also included.

An example would be the string: "destination":"Provence-Alpes-C\\\\303\\\\264te d\\'Azur"

Which prints as:

If I manually remove one of the \\ characters then Python happily interprets the string and it prints as:

There is some good stuff in this thread and although .decode('string_escape') works well on an individual snippet, when its part of the much longer string comprising thousands of records then it doesn't work.

I believe that I need a clever way to replace the \\\\ with \\ but for well documented reasons, .replace('\\\\', '\\') doesn't work.

In order to get the files to work at all I used a regex to remove all \\ followed by a number: re.sub(r'\\\\(?=[0-9])', '', g) - I'm thinking that an adaptation of this might be the way forward but the number needs to be dynamic as I don't know what it will be (ie using \\3 and \\2 for the example above isn't going to work')

Help appreciated.

Answer 1

Rather than have Python interpret \\ooo octal escapes, repair the JSON with a regular expression, then parse it as JSON. I did so before in similar circumstances

Your data has UTF-8 bytes escaped to octal \\ooo sequences, so you are looking for a more limited range of values here:

import re

invalid_escape = re.compile(r'\\([1-3][0-7]{2}|[1-7][0-7]?)')  # octal digits from 1 up to FF
def replace_with_codepoint(match):
    return chr(int(match.group(0)[1:], 8))

def repair(brokenjson):
    return invalid_escape.sub(replace_with_codepoint, brokenjson)

Demo:

>>> import json
>>> sample = '{"destination":"Provence-Alpes-C\\303\\264te d\'Azur"}'
>>> repair(sample)
'{"destination":"Provence-Alpes-C\xc3\xb4te d\'Azur"}'
>>> json.loads(repair(sample))
{u'destination': u"Provence-Alpes-C\xf4te d'Azur"}
>>> print json.loads(repair(sample))['destination']
Provence-Alpes-Côte d'Azur