ENH: GH34946 Check type of names argument to read_csv, read_table, read_fwf to not be a set.

Author: MJafarMashhadi

doc/source/whatsnew/v1.1.0.rst

@@ -1121,6 +1121,7 @@ Other
 - :class:`IntegerArray` now implements the ``sum`` operation (:issue:`33172`)
 - Bug in :class:`Tick` comparisons raising ``TypeError`` when comparing against timedelta-like objects (:issue:`34088`)
 - Bug in :class:`Tick` multiplication raising ``TypeError`` when multiplying by a float (:issue:`34486`)
+- Passing a `set` as `names` argument to :func:`pandas.read_csv`, :func:`pandas.read_table`, or :func:`pandas.read_fwf` will raise ``ValueError: Names should have consistent ordering. Consider a list instead.`` (:issue:`34946`)
 
 .. ---------------------------------------------------------------------------
 

pandas/io/parsers.py

@@ -397,7 +397,8 @@ def _validate_integer(name, val, min_val=0):
 
 def _validate_names(names):
     """
-    Raise ValueError if the `names` parameter contains duplicates.
+    Raise ValueError if the `names` parameter contains duplicates or has an
+    invalid data type.
 
     Parameters
     ----------
@@ -407,11 +408,15 @@ def _validate_names(names):
     Raises
     ------
     ValueError
-        If names are not unique.
+        If names are not unique or have incosistent ordering (e.g. set).
     """
     if names is not None:
         if len(names) != len(set(names)):
             raise ValueError("Duplicate names are not allowed.")
+        if not is_list_like(names, allow_sets=False):
+            raise ValueError(
+                "Names should have consistent ordering. Consider a list instead."
+            )
 
 
 def _read(filepath_or_buffer: FilePathOrBuffer, kwds):