JuliaCall doesn't work with pandas DataFrames that have categorical columns

[Wainberg]

JuliaCall doesn't work with pandas DataFrames that have categorical columns. Here's an example:

>>> import pandas as pd
>>> from juliacall import Main as jl
>>> jl.seval('using DataFrames')
>>> df = pd.DataFrame({'a': [1,2,3], 'b': ['x','y','z']})
>>> jl.DataFrame(df)  # works fine
<jl 3×2 DataFrame
 Row │ a      b
     │ Int64  String
─────┼───────────────
   1 │     1  x
   2 │     2  y
   3 │     3  z>
>>> jl.DataFrame(df.astype({'a': 'category'}))  # gives DimensionMismatch error?!
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/nethome/kcni/mwainberg/.julia/packages/PythonCall/DqZCE/src/jlwrap/any.jl", line 201, in __call__
    return self._jl_callmethod($(pyjl_methodnum(pyjlany_call)), args, kwargs)
juliacall.JuliaError: DimensionMismatch: column :a has length 16 and column :b has length 3
Stacktrace:
 [1] DataFrame(columns::Vector{AbstractVector}, colindex::DataFrames.Index; copycols::Bool)
   @ DataFrames ~/.julia/packages/DataFrames/a6np0/src/dataframe/dataframe.jl:192
 [2] fromcolumns(x::Tables.DictColumnTable, names::Vector{Symbol}; copycols::Nothing)
   @ DataFrames ~/.julia/packages/DataFrames/a6np0/src/other/tables.jl:36
 [3] DataFrame(x::PythonCall.PyPandasDataFrame; copycols::Nothing)
   @ DataFrames ~/.julia/packages/DataFrames/a6np0/src/other/tables.jl:60
 [4] DataFrame(x::PythonCall.PyPandasDataFrame)
   @ DataFrames ~/.julia/packages/DataFrames/a6np0/src/other/tables.jl:48
 [5] pyjlany_call(self::Type{DataFrame}, args_::PythonCall.Py, kwargs_::PythonCall.Py)
   @ PythonCall ~/.julia/packages/PythonCall/DqZCE/src/jlwrap/any.jl:31
 [6] _pyjl_callmethod(f::Any, self_::Ptr{PythonCall.C.PyObject}, args_::Ptr{PythonCall.C.PyObject}, nargs::Int64)
   @ PythonCall ~/.julia/packages/PythonCall/DqZCE/src/jlwrap/base.jl:69
 [7] _pyjl_callmethod(o::Ptr{PythonCall.C.PyObject}, args::Ptr{PythonCall.C.PyObject})
   @ PythonCall.C ~/.julia/packages/PythonCall/DqZCE/src/cpython/jlwrap.jl:47
>>> jl.DataFrame(df.astype({'b': 'category'}))   # gives internal SystemError in Python
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/nethome/kcni/mwainberg/.julia/packages/PythonCall/DqZCE/src/jlwrap/any.jl", line 201, in __call__
    return self._jl_callmethod($(pyjl_methodnum(pyjlany_call)), args, kwargs)
SystemError: null argument to internal routine
>>> jl.DataFrame(df.astype('category'))  # ditto
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/nethome/kcni/mwainberg/.julia/packages/PythonCall/DqZCE/src/jlwrap/any.jl", line 201, in __call__
    return self._jl_callmethod($(pyjl_methodnum(pyjlany_call)), args, kwargs)
SystemError: null argument to internal routine

[cjdoris]

Thanks, this is fixed on the main branch now (silly mistake).

I'll make a release in the next few days.