# Buggy code
def _setitem_single_block(self, indexer, value, name: str):
    """
    _setitem_with_indexer for the case when we have a single Block.
    """
    from pandas import Series

    info_axis = self.obj._info_axis_number
    item_labels = self.obj._get_axis(info_axis)

    if isinstance(indexer, tuple):
        # if we are setting on the info axis ONLY
        # set using those methods to avoid block-splitting
        # logic here
        if (
            len(indexer) > info_axis
            and is_integer(indexer[info_axis])
            and all(
                com.is_null_slice(idx)
                for i, idx in enumerate(indexer)
                if i != info_axis
            )
            and item_labels.is_unique
        ):
            self.obj[item_labels[indexer[info_axis]]] = value
            return

        indexer = maybe_convert_ix(*indexer)
    if (isinstance(value, ABCSeries) and name != "iloc") or isinstance(value, dict):
        # TODO(EA): ExtensionBlock.setitem this causes issues with
        # setting for extensionarrays that store dicts. Need to decide
        # if it's worth supporting that.
        value = self._align_series(indexer, Series(value))

    elif isinstance(value, ABCDataFrame) and name != "iloc":
        value = self._align_frame(indexer, value)

    # check for chained assignment
    self.obj._check_is_chained_assignment_possible()

    # actually do the set
    self.obj._mgr = self.obj._mgr.setitem(indexer=indexer, value=value)
    self.obj._maybe_update_cacher(clear=True)


# Traceback (ValueError)
Traceback (most recent call last):
File "c:\Users\leona\pandas\main.py", line 3, in <module>
df.loc[:, 'a'] = list(range(5))
File "c:\Users\leona\pandas\pandas\core\indexing.py", line 691, in __setitem__
iloc._setitem_with_indexer(indexer, value, self.name)
File "c:\Users\leona\pandas\pandas\core\indexing.py", line 1636, in _setitem_with_indexer
self._setitem_single_block(indexer, value, name)
File "c:\Users\leona\pandas\pandas\core\indexing.py", line 1862, in _setitem_single_block
self.obj._mgr = self.obj._mgr.setitem(indexer=indexer, value=value)
File "c:\Users\leona\pandas\pandas\core\internals\managers.py", line 565, in setitem
return self.apply("setitem", indexer=indexer, value=value)
File "c:\Users\leona\pandas\pandas\core\internals\managers.py", line 428, in apply
applied = getattr(b, f)(**kwargs)
File "c:\Users\leon\pandas\pandas\core\internals\blocks.py", line 1022, in setitem
values[indexer] = value
ValueError: cannot copy sequence with size 5 to array axis with dimension 0

# Fixed code
def _setitem_single_block(self, indexer, value, name: str):
    """
    _setitem_with_indexer for the case when we have a single Block.
    """
    from pandas import Series

    info_axis = self.obj._info_axis_number
    item_labels = self.obj._get_axis(info_axis)

    if isinstance(indexer, tuple):
        # if we are setting on the info axis ONLY
        # set using those methods to avoid block-splitting
        # logic here
        if (
            len(indexer) > info_axis
            and is_integer(indexer[info_axis])
            and all(
                com.is_null_slice(idx)
                for i, idx in enumerate(indexer)
                if i != info_axis
            )
        ):
            selected_item_labels = item_labels[indexer[info_axis]]
            if len(item_labels.get_indexer_for([selected_item_labels])) == 1:
                self.obj[selected_item_labels] = value
                return

        indexer = maybe_convert_ix(*indexer)
    if (isinstance(value, ABCSeries) and name != "iloc") or isinstance(value, dict):
        # TODO(EA): ExtensionBlock.setitem this causes issues with
        # setting for extensionarrays that store dicts. Need to decide
        # if it's worth supporting that.
        value = self._align_series(indexer, Series(value))

    elif isinstance(value, ABCDataFrame) and name != "iloc":
        value = self._align_frame(indexer, value)

    # check for chained assignment
    self.obj._check_is_chained_assignment_possible()

    # actually do the set
    self.obj._mgr = self.obj._mgr.setitem(indexer=indexer, value=value)
    self.obj._maybe_update_cacher(clear=True)