Misleading error for pd.read_msgpack

[smspillaz]

Code Sample, a copy-pastable example if possible

import pandas as pd
pd.read_msgpack('this/path/does/not/exist')

Problem description

Such an error is misleading because it suggests that there is a problem with the datatype being passed, not that the path does not exist. The error raised is:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File ".local/anaconda3/lib/python3.7/site-packages/pandas/io/packers.py", line 226, in read_msgpack
    raise ValueError('path_or_buf needs to be a string file path or file-like')
ValueError: path_or_buf needs to be a string file path or file-like

Expected Output

Raise an error indicating that the path was not found.

Output of pd.show_versions()

>>> pd.show_versions()

INSTALLED VERSIONS

commit: None
python: 3.7.3.final.0
python-bits: 64
OS: Linux
OS-release: 4.18.0-24-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

pandas: 0.24.2
pytest: 4.3.1
pip: 19.0.3
setuptools: 40.8.0
Cython: 0.29.6
numpy: 1.16.2
scipy: 1.2.1
pyarrow: None
xarray: None
IPython: 7.4.0
sphinx: 1.8.5
patsy: 0.5.1
dateutil: 2.8.0
pytz: 2018.9
blosc: None
bottleneck: 1.2.1
tables: 3.5.1
numexpr: 2.6.9
feather: None
matplotlib: 3.0.3
openpyxl: 2.6.1
xlrd: 1.2.0
xlwt: 1.3.0
xlsxwriter: 1.1.5
lxml.etree: 4.3.2
bs4: 4.7.1
html5lib: 1.0.1
sqlalchemy: 1.3.1
pymysql: None
psycopg2: None
jinja2: 2.10
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datarea

[TomAugspurger]

I think the first argument of read_msgpack can *also* be data. ``` In [4]: pd.read_msgpack(b'') /Users/taugspurger/Envs/pandas-dev/lib/python3.7/site-packages/IPython/core/interactiveshell.py:3296: FutureWarning: The read_msgpack is deprecated and will be removed in a future version. It is recommended to use pyarrow for on-the-wire transmission of pandas objects. exec(code_obj, self.user_global_ns, self.user_ns) Out[4]: [] ``` Regardless, I believe we're deprecating read_msgpack so this may not be worth changing.

…

On Mon, Jul 1, 2019 at 8:02 AM Sam Spilsbury ***@***.***> wrote: Code Sample, a copy-pastable example if possible import pandas as pd pd.read_msgpack('this/path/does/not/exist') Problem description Such an error is misleading because it suggests that there is a problem with the datatype being passed, not that the path does not exist. The error raised is: Traceback (most recent call last): File "<stdin>", line 1, in <module> File ".local/anaconda3/lib/python3.7/site-packages/pandas/io/packers.py", line 226, in read_msgpack raise ValueError('path_or_buf needs to be a string file path or file-like') ValueError: path_or_buf needs to be a string file path or file-like Expected Output Raise an error indicating that the path was not found. Output of pd.show_versions() >>> pd.show_versions() INSTALLED VERSIONS commit: None python: 3.7.3.final.0 python-bits: 64 OS: Linux OS-release: 4.18.0-24-generic machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: en_US.UTF-8 pandas: 0.24.2 pytest: 4.3.1 pip: 19.0.3 setuptools: 40.8.0 Cython: 0.29.6 numpy: 1.16.2 scipy: 1.2.1 pyarrow: None xarray: None IPython: 7.4.0 sphinx: 1.8.5 patsy: 0.5.1 dateutil: 2.8.0 pytz: 2018.9 blosc: None bottleneck: 1.2.1 tables: 3.5.1 numexpr: 2.6.9 feather: None matplotlib: 3.0.3 openpyxl: 2.6.1 xlrd: 1.2.0 xlwt: 1.3.0 xlsxwriter: 1.1.5 lxml.etree: 4.3.2 bs4: 4.7.1 html5lib: 1.0.1 sqlalchemy: 1.3.1 pymysql: None psycopg2: None jinja2: 2.10 s3fs: None fastparquet: None pandas_gbq: None pandas_datarea — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#27160?email_source=notifications&email_token=AAKAOIWGKYF5VVZUERGDRRTP5H54ZA5CNFSM4H4SFK22YY3PNVWWK3TUL52HS4DFUVEXG43VMWVGG33NNVSW45C7NFSM4G4UIWEA>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAKAOIVMPWSJDZCUCOO5F3TP5H54ZANCNFSM4H4SFK2Q> .

[jreback]

yeah this is true of several routines (e.g. read_json), there is an issue about this somewhere. but for msgpack since we are deprecated, this is out of scope (would take a reasonable patch though).

[jreback]

as PR is submitted :->

[simonjayhawkins]

I think the first argument of read_msgpack can also be data.

I think that assuming a string passed to pd.read_msgpack is a filepath and then raising if not found is OK?

the data as bytes works as intended.

the docs for pandas.DataFrame.to_msgpack are misleading https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.to_msgpack.html?highlight=to_msgpack#pandas-dataframe-to-msgpack suggest that a string is returned when bytes are returned...

path : string File path, buffer-like, or None
if None, return generated string

>>> import numpy as np
>>> import pandas as pd
>>> from pandas import DataFrame
>>> df = DataFrame(np.random.randn(10, 2))
>>>
>>>
>>> df.to_msgpack(None)
b'\x84\xa3typ\xadblock_manager\xa5klass\xa9DataFrame\xa4axes\x92\x86\xa3typ\xabrange_index\xa5klass\xaaRangeIndex\xa4name\xc0\xa5start\x00\xa4s
top\x02\xa4step\x01\x86\xa3typ\xabrange_index\xa5klass\xaaRangeIndex\xa4name\xc0\xa5start\x00\xa4stop\n\xa4step\x01\xa6blocks\x91\x86\xa4locs\x
86\xa3typ\xa7ndarray\xa5shape\x91\x02\xa4ndim\x01\xa5dtype\xa5int64\xa4data\xd8\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00
\x00\xa8compress\xc0\xa6values\xc7\xa0\x00A\x10\x94Z\x0f|\xd0?F]>R\xc7\xfc\xf5\xbf\xa4\xeb\xe2:\x07X\xc5\xbf&\x1bAje\t\xbb?\x98w9\x17:"\xe1?#\x
e4\xc9\xda\x86\xdf\xaf\xbf\xec\xe63K2\x03\xee\xbf\xad0%v\x11$\xda\xbf\xa1\x02@\xff\xb7\xc8\xff?\xb0G\x11\x02\x80\x13\xe1?)\xf8l\xcb~/\xd2?\xb2\
x17I\xeb\x91k\x03@\xbf\xfaj\xb2\x89\x14\xc2\xbf\xbd5\xba\xb3j\x1c\xed?u\xe504\x17\xaf\xd0\xbf\xc7\xa5\xc3\xf3\x12\xf1\xf4?\xe6\xf0\x05\xf2\xef\
xd6\x05@\xec\xeb\xd1\x80w}\xf0\xbfx\x94\x82\x10"U\xeb?.\xbdZI\x89X\xea?\xa5shape\x92\x02\n\xa5dtype\xa7float64\xa5klass\xaaFloatBlock\xa8compre
ss\xc0'
>>>
>>> pd.read_msgpack(df.to_msgpack(None))
sys:1: FutureWarning: The read_msgpack is deprecated and will be removed in a future version.
It is recommended to use pyarrow for on-the-wire transmission of pandas objects.
          0         1
0  0.257572  0.284149
1 -1.374214  2.427524
2 -0.166749 -0.141252
3  0.105612  0.909719
4  0.535428 -0.260687
5 -0.062252  1.308856
6 -0.937890  2.729950
7 -0.408451 -1.030632
8  1.986504  0.854142
9  0.533630  0.823308
>>>