read_json(lines=True) broken for s3 urls in Python 3 (v0.20.3)

[alph486]

Code Sample, a copy-pastable example if possible

Using Python

import pandas as pd
inputdf = pd.read_json(path_or_buf="s3://path/to/python-lines/file.json", lines=True)

The file is similar to:

{"url": "blah", "other": "blah"}
{"url": "blah", "other": "blah"}
{"url": "blah", "other": "blah"}

Problem description

When attempting to read a python lines file into a DataFrame using the s3 protocol, the above code will error with:

2017-08-08 11:06:14,225 - image_rank_csv - ERROR - initial_value must be str or None, not bytes
Traceback (most recent call last):
  File "image_rank_csv.py", line 62, in run
    inputdf = pd.read_json(path_or_buf="s3://path/to/python-lines/file.json", lines=True)
  File "...env/lib/python3.6/site-packages/pandas/io/json/json.py", line 347, in read_json
    lines = list(StringIO(json.strip()))
TypeError: initial_value must be str or None, not bytes

This works fine if the file is local, e.g.:

import pandas as pd
inputdf = pd.read_json(path_or_buf="/local/path/to/python-lines/file.json", lines=True)

Expected Output

Expect to successfully read the file and error above not to occur.

My current thinking is that when we get the file handle: https://github.com/pandas-dev/pandas/blob/v0.20.3/pandas/io/json/json.py#L333 , you delegate to s3fs, which documents that it only operates in Binary mode. Therefore when you read(): https://github.com/pandas-dev/pandas/blob/v0.20.3/pandas/io/json/json.py#L335, Therefore passing to StringIO will fail here: https://github.com/pandas-dev/pandas/blob/v0.20.3/pandas/io/json/json.py#L347 . Maybe it needs a different handler for BytesIO?

Output of pd.show_versions()

[paste the output of ``pd.show_versions()`` here below this line] ``` INSTALLED VERSIONS ------------------ commit: None python: 3.6.1.final.0 python-bits: 64 OS: Darwin OS-release: 16.6.0 machine: x86_64 processor: i386 byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: en_US.UTF-8

pandas: 0.20.3
pytest: None
pip: 9.0.1
setuptools: 36.2.7
Cython: None
numpy: 1.12.0
scipy: 0.19.1
xarray: None
IPython: None
sphinx: None
patsy: None
dateutil: 2.6.0
pytz: 2017.2
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: None
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
sqlalchemy: None
pymysql: None
psycopg2: 2.6.2 (dt dec pq3 ext lo64)
jinja2: None
s3fs: 0.1.2
pandas_gbq: None
pandas_datareader: None

</details>

[gfyoung]

Well we do have a BytesIO class in pandas.compat. If we can condition on the data returned to us, that would be reasonable I think.

[alph486]

@gfyoung I'm not intimately familiar with the codebase, but I have a (possibly naive) fix that just attempts to decode the json based on whatever encoding is. It seems to fix. Would you like to review if do a PR?

[gfyoung]

I'm not intimately familiar with the codebase

Don't worry, that's a pretty tall order 😄

Absolutely! Submit a PR, and we'll certainly review it.

[TomAugspurger]

FYI, here's how we handle it on the CSV side:

pandas/pandas/io/common.py

Line 401 in 3c833db

if compat.PY3 and is_text and\

that f would be an instance of S3File, which is one of the classes in need_text_wrapping. By the TextIOWrapper can go around buffer of bytes and it'll do the encoding. You might be able to reuse parts of that for read_json, or just do something similar.

[alph486]

Naive PR submitted ;) @gfyoung