@@ -794,12 +794,16 @@ def _get_backend_or_none(self):
794794return None if backend is rcsetup ._auto_backend_sentinel else backend
795795
796796def __delitem__ (self ,key ):
797+ if key not in self .validate :
798+ raise KeyError (
799+ f"{ key }
800+ f"a list of valid parameters)" )
797801try :
798802del self ._rcvalues [key ]
799803except KeyError as err :
800804raise KeyError (
801- f"{ key } is not a valid rc parameter (see rcParams.keys() for "
802- f"a list of valid parameters)" )from err
805+ f"No custom value set for { key } . Cannot delete default value. "
806+ )from err
803807
804808def __contains__ (self ,key ):
805809return key in self ._rcvalues
@@ -824,22 +828,6 @@ def __repr__(self):
824828def __str__ (self ):
825829return '\n ' .join (map ('{0[0]}: {0[1]}' .format ,sorted (self ._rcvalues .items ())))
826830
827- def pop (self ,key ):
828- keys ,depth = self ._split_key (key )
829- if depth == 1 :
830- if key in self ._single_key_set :
831- return self ._namespace_mapping ["default" ][key ]
832- else :
833- raise KeyError (
834- f"{ key }
835- f"a list of valid parameters)" )
836- elif depth == 2 :
837- return self ._namespace_mapping [keys [0 ]].pop (keys [1 ])
838-
839- def popitem (self ):
840- raise NotImplementedError (
841- "popitem is not implemented for RcParams." )
842-
843831@_api .deprecated ("3.8" )
844832def clear (self ):
845833pass
@@ -1037,8 +1025,8 @@ def rc_params_from_file(fname, fail_on_error=False, use_default_template=True):
10371025# (resulting in a normal `#backend: foo` line) in which case we should *not*
10381026# fill in _auto_backend_sentinel.
10391027rcParams .update (_rc_params_in_file (matplotlib_fname ()))
1040- rcParams ._rcvalues = rcParams ._rcvalues .new_child ()
10411028rcParams .setdefault ("backend" ,rcsetup ._auto_backend_sentinel )
1029+ rcParams ._rcvalues = rcParams ._rcvalues .new_child ()
10421030rcParamsOrig = rcParams .copy ()
10431031with _api .suppress_matplotlib_deprecation_warning ():
10441032# This also checks that all rcParams are indeed listed in the template.