Avoid columns computation on 'df.columns ='

Signed-off-by: Dmitry Chigarev <dmitry.chigarev@intel.com>

modin/core/dataframe/pandas/dataframe/dataframe.py

@@ -639,6 +639,7 @@ def _compute_axis_labels_and_lengths(self, axis: int, partitions=None):
         List of int
             Size of partitions alongside specified `axis`.
         """
+
         if partitions is None:
             partitions = self._partitions
         new_index, internal_idx = self._partition_mgr_cls.get_indices(axis, partitions)

modin/pandas/dataframe.py

@@ -2401,7 +2401,8 @@ def __setattr__(self, key, value):
         #   before it appears in __dict__.
         if key in ("_query_compiler", "_siblings", "_cache") or key in self.__dict__:
             pass
-        elif key in self and key not in dir(self):
+        # we have to check for the key in `dir(self)` first in order not to trigger columns computation
+        elif key not in dir(self) and key in self:
             self.__setitem__(key, value)
             # Note: return immediately so we don't keep this `key` as dataframe state.
             # `__getattr__` will return the columns not present in `dir(self)`, so we do not need

setup.cfg

@@ -12,7 +12,7 @@ tag_prefix =
 parentdir_prefix = modin-
 
 [tool:pytest]
-addopts = --disable-pytest-warnings --cov-config=setup.cfg --cov=modin --cov-append --cov-report=
+addopts = --disable-pytest-warnings
 xfail_strict=true
 markers =
     xfail_executions