HDFStore - raising an exception when complevel > 0 and complib is None

[joonro]

Code Sample, a copy-pastable example if possible

HDFStore = pd.HDFStore('mydata.ph5', mode='w', complevel=9)

Problem description

Hi,

It seems when complib is None, pd.HDFStore does not use any compression even though a user supplies complevel > 0. If there is no good default option for complib, then in my opinion, HDFStore should raise an exception when (complib is None) and (complevel > 0) instead. This is because clearly the user wants compression but it cannot be done - I think explicitly raising an exception is better than silently ignoring the option.

Output of pd.show_versions()

pd.show_versions()

INSTALLED VERSIONS

commit: None
python: 3.5.2.final.0
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 62 Stepping 4, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.19.2
nose: 1.3.7
pip: 9.0.1
setuptools: 27.2.0
Cython: 0.24.1
numpy: 1.11.3
scipy: 0.18.1
statsmodels: 0.6.1
xarray: 0.9.1
IPython: 5.1.0
sphinx: 1.4.6
patsy: 0.4.1
dateutil: 2.5.3
pytz: 2016.6.1
blosc: None
bottleneck: 1.1.0
tables: 3.2.2
numexpr: 2.6.1
matplotlib: 1.5.3
openpyxl: 2.3.2
xlrd: 1.0.0
xlwt: 1.1.2
xlsxwriter: 0.9.3
lxml: 3.6.4
bs4: 4.5.1
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: 1.0.13
pymysql: None
psycopg2: None
jinja2: 2.8
boto: 2.42.0
pandas_datareader: None

[jreback]

xref to #14478

[jreback]

for sure would take bug fixes around this (and related issues)!. please make sure to have tests!

[joonro]

I see - thanks for the pointers!

[linebp]

If no-one is working on this, I can give it a try?

I looked at the __init__ in class HDFStore and #14478. Can the default in default_complib in pytables tables.filters module be used as a default value here too? If this is the way to go, it is perhaps best to fix #14478 first (avoiding the possible issue of using a default that is not otherwise an option)?

Maybe an exception or some pandas defined default value is the way to go instead?

Where would the tests for this belong?

[jreback]

this is orthogonal to #14478 though easy enough to fix both. tests are in pandas/tests/io/test_pytables.py