@@ -289,7 +289,7 @@ def get(self, timeout=None):
289289 try :
290290 return self ._result
291291 except AttributeError :
292- raise self ._exc
292+ raise self ._exc from None
293293
294294 def waitfinish (self , timeout = None ):
295295 if not self ._result_ready .wait (timeout ):
@@ -528,7 +528,7 @@ def from_io(io):
528528 if not header :
529529 raise EOFError ("empty read" )
530530 except EOFError as e :
531- raise EOFError ("couldn't load message header, " + e .args [0 ])
531+ raise EOFError ("couldn't load message header, " + e .args [0 ]) from None
532532 msgtype , channel , payload = struct .unpack ("!bii" , header )
533533 return Message (msgtype , channel , io .read (payload ))
534534
@@ -542,9 +542,7 @@ def received(self, gateway):
542542
543543 def __repr__ (self ):
544544 name = self ._types [self .msgcode ][0 ]
545- return "<Message {} channel={} lendata={}>" .format (
546- name , self .channelid , len (self .data )
547- )
545+ return f"<Message { name } channel={ self .channelid } lendata={ len (self .data )} >"
548546
549547 def _status (message , gateway ):
550548 # we use the channelid to send back information
@@ -851,7 +849,7 @@ def receive(self, timeout=None):
851849 try :
852850 x = itemqueue .get (timeout = timeout )
853851 except self .gateway .execmodel .queue .Empty :
854- raise self .TimeoutError ("no item after %r seconds" % timeout )
852+ raise self .TimeoutError ("no item after %r seconds" % timeout ) from None
855853 if x is ENDMARKER :
856854 itemqueue .put (x ) # for other receivers
857855 raise self ._getremoteerror () or EOFError ()
@@ -865,7 +863,7 @@ def next(self):
865863 try :
866864 return self .receive ()
867865 except EOFError :
868- raise StopIteration
866+ raise StopIteration from None
869867
870868 __next__ = next
871869
@@ -1108,7 +1106,7 @@ def _send(self, msgcode, channelid=0, data=b""):
11081106 except (OSError , ValueError ) as e :
11091107 self ._trace ("failed to send" , message , e )
11101108 # ValueError might be because the IO is already closed
1111- raise OSError ("cannot send (already closed?)" )
1109+ raise OSError ("cannot send (already closed?)" ) from e
11121110
11131111 def _local_schedulexec (self , channel , sourcetask ):
11141112 channel .close ("execution disallowed" )
@@ -1316,12 +1314,12 @@ def load(self, versioned=False):
13161314 loader = self .num2func [opcode ]
13171315 except KeyError :
13181316 raise LoadError (
1319- "unknown opcode %r - " " wire protocol corruption?" % ( opcode ,)
1320- )
1317+ f "unknown opcode { opcode !r } - wire protocol corruption?"
1318+ ) from None
13211319 loader (self )
13221320 except _Stop :
13231321 if len (self .stack ) != 1 :
1324- raise LoadError ("internal unserialization error" )
1322+ raise LoadError ("internal unserialization error" ) from None
13251323 return self .stack .pop (0 )
13261324 else :
13271325 raise LoadError ("didn't get STOP" )
@@ -1550,7 +1548,7 @@ def _save(self, obj):
15501548 methodname = "save_" + tp .__name__
15511549 meth = getattr (self .__class__ , methodname , None )
15521550 if meth is None :
1553- raise DumpError (f"can't serialize { tp } " )
1551+ raise DumpError (f"can't serialize { tp } " ) from None
15541552 dispatch = self ._dispatch [tp ] = meth
15551553 dispatch (self , obj )
15561554
@@ -1574,8 +1572,8 @@ def save_str(self, s):
15741572 def _write_unicode_string (self , s ):
15751573 try :
15761574 as_bytes = s .encode ("utf-8" )
1577- except UnicodeEncodeError :
1578- raise DumpError ("strings must be utf-8 encodable" )
1575+ except UnicodeEncodeError as e :
1576+ raise DumpError ("strings must be utf-8 encodable" ) from e
15791577 self ._write_byte_sequence (as_bytes )
15801578
15811579 def _write_byte_sequence (self , bytes_ ):
@@ -1593,7 +1591,7 @@ def _save_integral(self, i, short_op, long_op):
15931591 def save_int (self , i ):
15941592 self ._save_integral (i , opcode .INT , opcode .LONGINT )
15951593
1596- def save_long (self , l ): # noqa:E741
1594+ def save_long (self , l ):
15971595 self ._save_integral (l , opcode .LONG , opcode .LONGLONG )
15981596
15991597 def save_float (self , flt ):
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