df.head()[['Country','GDP']]
Country 	GDP
0 	Abkhazia 	NaN
1 	Afghanistan 	1.946902e+10
2 	Albania 	1.186387e+10
3 	Algeria 	1.590490e+11
4 	American Samoa 	NaN

un = ['Afghanistan',
 'Albania',
 'Algeria',
 'Andorra',
 'Angola',
 'Antigua and Barbuda', ... # etc. to Zimbabwe
]
df.query(f"Country in {un}")
# 
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[4], line 1
----> 1 df.query(f'` in {un}')

File ~/anaconda3/envs/py13/lib/python3.13/site-packages/pandas/core/frame.py:4834, in DataFrame.query(self, expr, inplace, **kwargs)
   4832 kwargs["level"] = kwargs.pop("level", 0) + 1
   4833 kwargs["target"] = None
-> 4834 res = self.eval(expr, **kwargs)
   4836 try:
   4837     result = self.loc[res]

File ~/anaconda3/envs/py13/lib/python3.13/site-packages/pandas/core/frame.py:4954, in DataFrame.eval(self, expr, inplace, **kwargs)
   4952 kwargs["level"] = kwargs.pop("level", 0) + 1
   4953 index_resolvers = self._get_index_resolvers()
-> 4954 column_resolvers = self._get_cleaned_column_resolvers()
   4955 resolvers = column_resolvers, index_resolvers
   4956 if "target" not in kwargs:

File ~/anaconda3/envs/py13/lib/python3.13/site-packages/pandas/core/generic.py:663, in NDFrame._get_cleaned_column_resolvers(self)
    659 if isinstance(self, ABCSeries):
    660     return {clean_column_name(self.name): self}
    662 return {
--> 663     clean_column_name(k): Series(
    664         v, copy=False, index=self.index, name=k, dtype=self.dtypes[k]
    665     ).__finalize__(self)
    666     for k, v in zip(self.columns, self._iter_column_arrays())
    667     if not isinstance(k, int)
    668 }

File ~/anaconda3/envs/py13/lib/python3.13/site-packages/pandas/core/series.py:496, in Series.__init__(self, data, index, dtype, name, copy, fastpath)
    493     index = ensure_index(index)
    495 if dtype is not None:
--> 496     dtype = self._validate_dtype(dtype)
    498 if data is None:
    499     index = index if index is not None else default_index(0)

File ~/anaconda3/envs/py13/lib/python3.13/site-packages/pandas/core/generic.py:519, in NDFrame._validate_dtype(cls, dtype)
    517 """validate the passed dtype"""
    518 if dtype is not None:
--> 519     dtype = pandas_dtype(dtype)
    521     # a compound dtype
    522     if dtype.kind == "V":

File ~/anaconda3/envs/py13/lib/python3.13/site-packages/pandas/core/dtypes/common.py:1684, in pandas_dtype(dtype)
   1682     return npdtype
   1683 elif npdtype.kind == "O":
-> 1684     raise TypeError(f"dtype '{dtype}' not understood")
   1686 return npdtype

TypeError: dtype '    object
    object
    object
    object
    object
    object
    object
    object
    object
dtype: object' not understood