Avoid deprecated pandas is_categorical_dtype API

[matthewwardrop]

This patch side-steps the issues addressed by #198 and #199, but avoiding recently deprecated APIs.

[bashtage]

Pretty sure this will not work on old pandas, e.g., those that work with python 2.7

[matthewwardrop]

Hmmm... I presume this was for an older commit, since this should work pretty universally as is. I cannot remember exactly what the old code looked like, but I'm going to assume you were right :).

[bashtage]

I think you could start with hasattr(pandas, "CategoricalDType") and then the lambda

Failing this, you could do elif hasattr(pandas, "api"), and then _pandas_is_categorical_dtype = getattr(pandas.api.types, "is_categorical_dtype", None),

finally, else, None.

Something like

# default value
_pandas_is_categorical_dtype  = None
if hasattr(pandas, "CategoricalDType"):
    _pandas_is_categorical_dtype = lambda x: isinstance(x, pandas.CategoricalDType)
elif hasattr(pandas, "api") and getattr(pandas.api.types, "is_categorical_dtype", None) is not None:
    def silenced_is_categorigal_type(typ):
        with warnings.catch_warnings():
            warnings.filterwarnings('ignore')
            return pandas.api.types.is_categorical_dtype(typ)

    _pandas_is_categorical_dtype = silenced_is_categorigal_type

[matthewwardrop]

Yeah... still fiddling with this a bit... delving into pandas ancient history and seeing where things were introduced.

[matthewwardrop]

Why do we need the warnings filter?

[bashtage]

I reckon just throw it in to make sure noting comes up. We know if is there then it will either FutureWarn, DepreactionWarn, or nothing. The first two are just noise.

[matthewwardrop]

The current code looks like:

have_pandas_categorical = (have_pandas and hasattr(pandas, "Categorical"))
if not have_pandas:
    _pandas_is_categorical_dtype = None
else:
    if hasattr(pandas, "CategoricalDtype"):  # pandas >= 0.25
        _pandas_is_categorical_dtype = lambda x: isinstance(getattr(x, "dtype", x), pandas.CategoricalDtype)
    elif hasattr(pandas, "api"):  # pandas >= 0.19
        _pandas_is_categorical_dtype = getattr(pandas.api.types, "is_categorical_dtype", None)
    else:  # pandas <=0.18
        _pandas_is_categorical_dtype = getattr(pandas.core.common,
                                               "is_categorical_dtype", None)
have_pandas_categorical_dtype = _pandas_is_categorical_dtype is not None

I don't see how we could ever generate a deprecation warning... so I'll just drop the warnings filter for now. It's arcane enough as it is :).

[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (ae3e8cb) 98.37% compared to head (f23e3bc) 98.46%.
Report is 1 commits behind head on master.

Files	Patch %	Lines
patsy/util.py	50.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #204      +/-   ##
==========================================
+ Coverage   98.37%   98.46%   +0.09%     
==========================================
  Files          30       30              
  Lines        3140     3133       -7     
  Branches      695      693       -2     
==========================================
- Hits         3089     3085       -4     
+ Misses         26       25       -1     
+ Partials       25       23       -2     

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