Bytecode analysis¶

The bytecode analysis API allows pieces of Python code to be wrapped in aBytecode object that provides easy access to details of the compiledcode.

classdis.Bytecode(x,*,first_line=None,current_offset=None)¶

Analyse the bytecode corresponding to a function, generator, asynchronousgenerator, coroutine, method, string of source code, or a code object (asreturned bycompile()).

This is a convenience wrapper around many of the functions listed below, mostnotablyget_instructions(), as iterating over aBytecodeinstance yields the bytecode operations asInstruction instances.

Iffirst_line is notNone, it indicates the line number that should bereported for the first source line in the disassembled code. Otherwise, thesource line information (if any) is taken directly from the disassembled codeobject.

Ifcurrent_offset is notNone, it refers to an instruction offset in thedisassembled code. Setting this meansdis() will display a “currentinstruction” marker against the specified opcode.

classmethodfrom_traceback(tb)¶

Construct aBytecode instance from the given traceback, settingcurrent_offset to the instruction responsible for the exception.

codeobj¶

The compiled code object.

first_line¶

The first source line of the code object (if available)

dis()¶

Return a formatted view of the bytecode operations (the same as printed bydis.dis(), but returned as a multi-line string).

info()¶

Return a formatted multi-line string with detailed information about thecode object, likecode_info().

Changed in version 3.7:This can now handle coroutine and asynchronous generator objects.

Example:

>>>bytecode=dis.Bytecode(myfunc)>>>forinstrinbytecode:...print(instr.opname)...LOAD_GLOBALLOAD_FASTCALL_FUNCTIONRETURN_VALUE

Analysis functions¶

Thedis module also defines the following analysis functions that convertthe input directly to the desired output. They can be useful if only a singleoperation is being performed, so the intermediate analysis object isn’t useful:

dis.code_info(x)¶

Return a formatted multi-line string with detailed code object informationfor the supplied function, generator, asynchronous generator, coroutine,method, source code string or code object.

Note that the exact contents of code info strings are highly implementationdependent and they may change arbitrarily across Python VMs or Pythonreleases.

New in version 3.2.

Changed in version 3.7:This can now handle coroutine and asynchronous generator objects.

dis.show_code(x,*,file=None)¶

Print detailed code object information for the supplied function, method,source code string or code object tofile (orsys.stdout iffileis not specified).

This is a convenient shorthand forprint(code_info(x),file=file),intended for interactive exploration at the interpreter prompt.

New in version 3.2.

Changed in version 3.4:Addedfile parameter.

dis.dis(x=None,*,file=None,depth=None)¶

Disassemble thex object.x can denote either a module, a class, amethod, a function, a generator, an asynchronous generator, a coroutine,a code object, a string of source code or a byte sequence of raw bytecode.For a module, it disassembles all functions. For a class, it disassemblesall methods (including class and static methods). For a code object orsequence of raw bytecode, it prints one line per bytecode instruction.It also recursively disassembles nested code objects (the code ofcomprehensions, generator expressions and nested functions, and the codeused for building nested classes).Strings are first compiled to code objects with thecompile()built-in function before being disassembled. If no object is provided, thisfunction disassembles the last traceback.

The disassembly is written as text to the suppliedfile argument ifprovided and tosys.stdout otherwise.

The maximal depth of recursion is limited bydepth unless it isNone.depth=0 means no recursion.

Changed in version 3.4:Addedfile parameter.

Changed in version 3.7:Implemented recursive disassembling and addeddepth parameter.

Changed in version 3.7:This can now handle coroutine and asynchronous generator objects.

dis.distb(tb=None,*,file=None)¶

Disassemble the top-of-stack function of a traceback, using the lasttraceback if none was passed. The instruction causing the exception isindicated.

The disassembly is written as text to the suppliedfile argument ifprovided and tosys.stdout otherwise.

Changed in version 3.4:Addedfile parameter.

dis.disassemble(code,lasti=-1,*,file=None)¶

dis.disco(code,lasti=-1,*,file=None)¶

Disassemble a code object, indicating the last instruction iflasti wasprovided. The output is divided in the following columns:

1. the line number, for the first instruction of each line

2. the current instruction, indicated as-->,

3. a labelled instruction, indicated with>>,

4. the address of the instruction,

5. the operation code name,

6. operation parameters, and

7. interpretation of the parameters in parentheses.

The parameter interpretation recognizes local and global variable names,constant values, branch targets, and compare operators.

The disassembly is written as text to the suppliedfile argument ifprovided and tosys.stdout otherwise.

Changed in version 3.4:Addedfile parameter.

dis.get_instructions(x,*,first_line=None)¶

Return an iterator over the instructions in the supplied function, method,source code string or code object.

The iterator generates a series ofInstruction named tuples givingthe details of each operation in the supplied code.

Iffirst_line is notNone, it indicates the line number that should bereported for the first source line in the disassembled code. Otherwise, thesource line information (if any) is taken directly from the disassembled codeobject.

New in version 3.4.

dis.findlinestarts(code)¶

This generator function uses theco_firstlineno andco_lnotabattributes of the code objectcode to find the offsets which are starts oflines in the source code. They are generated as(offset,lineno) pairs.SeeObjects/lnotab_notes.txt for theco_lnotab format andhow to decode it.

Changed in version 3.6:Line numbers can be decreasing. Before, they were always increasing.

dis.findlabels(code)¶

Detect all offsets in the raw compiled bytecode stringcode which are jump targets, andreturn a list of these offsets.

dis.stack_effect(opcode,oparg=None,*,jump=None)¶

Compute the stack effect ofopcode with argumentoparg.

If the code has a jump target andjump isTrue,stack_effect()will return the stack effect of jumping. Ifjump isFalse,it will return the stack effect of not jumping. And ifjump isNone (default), it will return the maximal stack effect of both cases.

New in version 3.4.

Changed in version 3.8:Addedjump parameter.

Python Bytecode Instructions¶

Theget_instructions() function andBytecode class providedetails of bytecode instructions asInstruction instances:

classdis.Instruction¶

Details for a bytecode operation

opcode¶

numeric code for operation, corresponding to the opcode values listedbelow and the bytecode values in theOpcode collections.

opname¶

human readable name for operation

arg¶

numeric argument to operation (if any), otherwiseNone

argval¶

resolved arg value (if known), otherwise same as arg

argrepr¶

human readable description of operation argument

offset¶

start index of operation within bytecode sequence

starts_line¶

line started by this opcode (if any), otherwiseNone

is_jump_target¶

True if other code jumps to here, otherwiseFalse

New in version 3.4.

The Python compiler currently generates the following bytecode instructions.

General instructions

NOP¶

Do nothing code. Used as a placeholder by the bytecode optimizer.

POP_TOP¶

Removes the top-of-stack (TOS) item.

ROT_TWO¶

Swaps the two top-most stack items.

ROT_THREE¶

Lifts second and third stack item one position up, moves top down to positionthree.

ROT_FOUR¶

Lifts second, third and fourth stack items one position up, moves top downto position four.

New in version 3.8.

DUP_TOP¶

Duplicates the reference on top of the stack.

New in version 3.2.

DUP_TOP_TWO¶

Duplicates the two references on top of the stack, leaving them in thesame order.

New in version 3.2.

Unary operations

Unary operations take the top of the stack, apply the operation, and push theresult back on the stack.

UNARY_POSITIVE¶

ImplementsTOS=+TOS.

UNARY_NEGATIVE¶

ImplementsTOS=-TOS.

UNARY_NOT¶

ImplementsTOS=notTOS.

UNARY_INVERT¶

ImplementsTOS=~TOS.

GET_ITER¶

ImplementsTOS=iter(TOS).

GET_YIELD_FROM_ITER¶

IfTOS is agenerator iterator orcoroutine objectit is left as is. Otherwise, implementsTOS=iter(TOS).

New in version 3.5.

Binary operations

Binary operations remove the top of the stack (TOS) and the second top-moststack item (TOS1) from the stack. They perform the operation, and put theresult back on the stack.

BINARY_POWER¶

ImplementsTOS=TOS1**TOS.

BINARY_MULTIPLY¶

ImplementsTOS=TOS1*TOS.

BINARY_MATRIX_MULTIPLY¶

ImplementsTOS=TOS1@TOS.

New in version 3.5.

BINARY_FLOOR_DIVIDE¶

ImplementsTOS=TOS1//TOS.

BINARY_TRUE_DIVIDE¶

ImplementsTOS=TOS1/TOS.

BINARY_MODULO¶

ImplementsTOS=TOS1%TOS.

BINARY_ADD¶

ImplementsTOS=TOS1+TOS.

BINARY_SUBTRACT¶

ImplementsTOS=TOS1-TOS.

BINARY_SUBSCR¶

ImplementsTOS=TOS1[TOS].

BINARY_LSHIFT¶

ImplementsTOS=TOS1<<TOS.

BINARY_RSHIFT¶

ImplementsTOS=TOS1>>TOS.

BINARY_AND¶

ImplementsTOS=TOS1&TOS.

BINARY_XOR¶

ImplementsTOS=TOS1^TOS.

BINARY_OR¶

ImplementsTOS=TOS1|TOS.

In-place operations

In-place operations are like binary operations, in that they remove TOS andTOS1, and push the result back on the stack, but the operation is done in-placewhen TOS1 supports it, and the resulting TOS may be (but does not have to be)the original TOS1.

INPLACE_POWER¶

Implements in-placeTOS=TOS1**TOS.

INPLACE_MULTIPLY¶

Implements in-placeTOS=TOS1*TOS.

INPLACE_MATRIX_MULTIPLY¶

Implements in-placeTOS=TOS1@TOS.

New in version 3.5.

INPLACE_FLOOR_DIVIDE¶

Implements in-placeTOS=TOS1//TOS.

INPLACE_TRUE_DIVIDE¶

Implements in-placeTOS=TOS1/TOS.

INPLACE_MODULO¶

Implements in-placeTOS=TOS1%TOS.

INPLACE_ADD¶

Implements in-placeTOS=TOS1+TOS.

INPLACE_SUBTRACT¶

Implements in-placeTOS=TOS1-TOS.

INPLACE_LSHIFT¶

Implements in-placeTOS=TOS1<<TOS.

INPLACE_RSHIFT¶

Implements in-placeTOS=TOS1>>TOS.

INPLACE_AND¶

Implements in-placeTOS=TOS1&TOS.

INPLACE_XOR¶

Implements in-placeTOS=TOS1^TOS.

INPLACE_OR¶

Implements in-placeTOS=TOS1|TOS.

STORE_SUBSCR¶

ImplementsTOS1[TOS]=TOS2.

DELETE_SUBSCR¶

ImplementsdelTOS1[TOS].

Coroutine opcodes

GET_AWAITABLE¶

ImplementsTOS=get_awaitable(TOS), whereget_awaitable(o)returnso ifo is a coroutine object or a generator object withthe CO_ITERABLE_COROUTINE flag, or resolveso.__await__.

New in version 3.5.

GET_AITER¶

ImplementsTOS=TOS.__aiter__().

New in version 3.5.

Changed in version 3.7:Returning awaitable objects from__aiter__ is no longersupported.

GET_ANEXT¶

ImplementsPUSH(get_awaitable(TOS.__anext__())). SeeGET_AWAITABLEfor details aboutget_awaitable

New in version 3.5.

END_ASYNC_FOR¶

Terminates anasyncfor loop. Handles an exception raisedwhen awaiting a next item. If TOS isStopAsyncIteration pop 7values from the stack and restore the exception state using the secondthree of them. Otherwise re-raise the exception using the three valuesfrom the stack. An exception handler block is removed from the block stack.

New in version 3.8.

BEFORE_ASYNC_WITH¶

Resolves__aenter__ and__aexit__ from the object on top of thestack. Pushes__aexit__ and result of__aenter__() to the stack.

New in version 3.5.

SETUP_ASYNC_WITH¶

Creates a new frame object.

New in version 3.5.

Miscellaneous opcodes

PRINT_EXPR¶

Implements the expression statement for the interactive mode. TOS is removedfrom the stack and printed. In non-interactive mode, an expression statementis terminated withPOP_TOP.

SET_ADD(i)¶

Callsset.add(TOS1[-i],TOS). Used to implement set comprehensions.

LIST_APPEND(i)¶

Callslist.append(TOS1[-i],TOS). Used to implement list comprehensions.

MAP_ADD(i)¶

Callsdict.__setitem__(TOS1[-i],TOS1,TOS). Used to implement dictcomprehensions.

New in version 3.1.

Changed in version 3.8:Map value is TOS and map key is TOS1. Before, those were reversed.

For all of theSET_ADD,LIST_APPEND andMAP_ADDinstructions, while the added value or key/value pair is popped off, thecontainer object remains on the stack so that it is available for furtheriterations of the loop.

RETURN_VALUE¶

Returns with TOS to the caller of the function.

YIELD_VALUE¶

Pops TOS and yields it from agenerator.

YIELD_FROM¶

Pops TOS and delegates to it as a subiterator from agenerator.

New in version 3.3.

SETUP_ANNOTATIONS¶

Checks whether__annotations__ is defined inlocals(), if not it isset up to an emptydict. This opcode is only emitted if a classor module body containsvariable annotationsstatically.

New in version 3.6.

IMPORT_STAR¶

Loads all symbols not starting with'_' directly from the module TOS tothe local namespace. The module is popped after loading all names. Thisopcode implementsfrommoduleimport*.

POP_BLOCK¶

Removes one block from the block stack. Per frame, there is a stack ofblocks, denotingtry statements, and such.

POP_EXCEPT¶

Removes one block from the block stack. The popped block must be an exceptionhandler block, as implicitly created when entering an except handler. Inaddition to popping extraneous values from the frame stack, the last threepopped values are used to restore the exception state.

POP_FINALLY(preserve_tos)¶

Cleans up the value stack and the block stack. Ifpreserve_tos is not0 TOS first is popped from the stack and pushed on the stack afterperforming other stack operations:

• If TOS isNULL or an integer (pushed byBEGIN_FINALLYorCALL_FINALLY) it is popped from the stack.

• If TOS is an exception type (pushed when an exception has been raised)6 values are popped from the stack, the last three popped values areused to restore the exception state. An exception handler block isremoved from the block stack.

It is similar toEND_FINALLY, but doesn’t change the bytecodecounter nor raise an exception. Used for implementingbreak,continue andreturn in thefinally block.

New in version 3.8.

BEGIN_FINALLY¶

PushesNULL onto the stack for using it inEND_FINALLY,POP_FINALLY,WITH_CLEANUP_START andWITH_CLEANUP_FINISH. Starts thefinally block.

New in version 3.8.

END_FINALLY¶

Terminates afinally clause. The interpreter recalls whether theexception has to be re-raised or execution has to be continued depending onthe value of TOS.

• If TOS isNULL (pushed byBEGIN_FINALLY) continue fromthe next instruction. TOS is popped.

• If TOS is an integer (pushed byCALL_FINALLY), sets thebytecode counter to TOS. TOS is popped.

• If TOS is an exception type (pushed when an exception has been raised)6 values are popped from the stack, the first three popped values areused to re-raise the exception and the last three popped values are usedto restore the exception state. An exception handler block is removedfrom the block stack.

LOAD_BUILD_CLASS¶

Pushesbuiltins.__build_class__() onto the stack. It is later calledbyCALL_FUNCTION to construct a class.

SETUP_WITH(delta)¶

This opcode performs several operations before a with block starts. First,it loads__exit__() from the context manager and pushes it ontothe stack for later use byWITH_CLEANUP_START. Then,__enter__() is called, and a finally block pointing todeltais pushed. Finally, the result of calling the__enter__() method is pushed ontothe stack. The next opcode will either ignore it (POP_TOP), orstore it in (a) variable(s) (STORE_FAST,STORE_NAME, orUNPACK_SEQUENCE).

New in version 3.2.

WITH_CLEANUP_START¶

Starts cleaning up the stack when awith statement block exits.

At the top of the stack are eitherNULL (pushed byBEGIN_FINALLY) or 6 values pushed if an exception has beenraised in the with block. Below is the context manager’s__exit__() or__aexit__() bound method.

If TOS isNULL, callsSECOND(None,None,None),removes the function from the stack, leaving TOS, and pushesNoneto the stack. Otherwise callsSEVENTH(TOP,SECOND,THIRD),shifts the bottom 3 values of the stack down, replaces the empty spotwithNULL and pushes TOS. Finally pushes the result of the call.

WITH_CLEANUP_FINISH¶

Finishes cleaning up the stack when awith statement block exits.

TOS is result of__exit__() or__aexit__() function call pushedbyWITH_CLEANUP_START. SECOND isNone or an exception type(pushed when an exception has been raised).

Pops two values from the stack. If SECOND is not None and TOS is trueunwinds the EXCEPT_HANDLER block which was created when the exceptionwas caught and pushesNULL to the stack.

All of the following opcodes use their arguments.

STORE_NAME(namei)¶

Implementsname=TOS.namei is the index ofname in the attributeco_names of the code object. The compiler tries to useSTORE_FAST orSTORE_GLOBAL if possible.

DELETE_NAME(namei)¶

Implementsdelname, wherenamei is the index intoco_namesattribute of the code object.

UNPACK_SEQUENCE(count)¶

Unpacks TOS intocount individual values, which are put onto the stackright-to-left.

UNPACK_EX(counts)¶

Implements assignment with a starred target: Unpacks an iterable in TOS intoindividual values, where the total number of values can be smaller than thenumber of items in the iterable: one of the new values will be a list of allleftover items.

The low byte ofcounts is the number of values before the list value, thehigh byte ofcounts the number of values after it. The resulting valuesare put onto the stack right-to-left.

STORE_ATTR(namei)¶

ImplementsTOS.name=TOS1, wherenamei is the index of name inco_names.

DELETE_ATTR(namei)¶

ImplementsdelTOS.name, usingnamei as index intoco_names.

STORE_GLOBAL(namei)¶

Works asSTORE_NAME, but stores the name as a global.

DELETE_GLOBAL(namei)¶

Works asDELETE_NAME, but deletes a global name.

LOAD_CONST(consti)¶

Pushesco_consts[consti] onto the stack.

LOAD_NAME(namei)¶

Pushes the value associated withco_names[namei] onto the stack.

BUILD_TUPLE(count)¶

Creates a tuple consumingcount items from the stack, and pushes theresulting tuple onto the stack.

BUILD_LIST(count)¶

Works asBUILD_TUPLE, but creates a list.

BUILD_SET(count)¶

Works asBUILD_TUPLE, but creates a set.

BUILD_MAP(count)¶

Pushes a new dictionary object onto the stack. Pops2*count itemsso that the dictionary holdscount entries:{...,TOS3:TOS2,TOS1:TOS}.

Changed in version 3.5:The dictionary is created from stack items instead of creating anempty dictionary pre-sized to holdcount items.

BUILD_CONST_KEY_MAP(count)¶

The version ofBUILD_MAP specialized for constant keys. Pops thetop element on the stack which contains a tuple of keys, then starting fromTOS1, popscount values to form values in the built dictionary.

New in version 3.6.

BUILD_STRING(count)¶

Concatenatescount strings from the stack and pushes the resulting stringonto the stack.

New in version 3.6.

BUILD_TUPLE_UNPACK(count)¶

Popscount iterables from the stack, joins them in a single tuple,and pushes the result. Implements iterable unpacking in tupledisplays(*x,*y,*z).

New in version 3.5.

BUILD_TUPLE_UNPACK_WITH_CALL(count)¶

This is similar toBUILD_TUPLE_UNPACK,but is used forf(*x,*y,*z) call syntax. The stack item at positioncount+1 should be the corresponding callablef.

New in version 3.6.

BUILD_LIST_UNPACK(count)¶

This is similar toBUILD_TUPLE_UNPACK, but pushes a listinstead of tuple. Implements iterable unpacking in listdisplays[*x,*y,*z].

New in version 3.5.

BUILD_SET_UNPACK(count)¶

This is similar toBUILD_TUPLE_UNPACK, but pushes a setinstead of tuple. Implements iterable unpacking in setdisplays{*x,*y,*z}.

New in version 3.5.

BUILD_MAP_UNPACK(count)¶

Popscount mappings from the stack, merges them into a single dictionary,and pushes the result. Implements dictionary unpacking in dictionarydisplays{**x,**y,**z}.

New in version 3.5.

BUILD_MAP_UNPACK_WITH_CALL(count)¶

This is similar toBUILD_MAP_UNPACK,but is used forf(**x,**y,**z) call syntax. The stack item atpositioncount+2 should be the corresponding callablef.

New in version 3.5.

Changed in version 3.6:The position of the callable is determined by adding 2 to the opcodeargument instead of encoding it in the second byte of the argument.

LOAD_ATTR(namei)¶

Replaces TOS withgetattr(TOS,co_names[namei]).

COMPARE_OP(opname)¶

Performs a Boolean operation. The operation name can be found incmp_op[opname].

IMPORT_NAME(namei)¶

Imports the moduleco_names[namei]. TOS and TOS1 are popped and providethefromlist andlevel arguments of__import__(). The moduleobject is pushed onto the stack. The current namespace is not affected: fora proper import statement, a subsequentSTORE_FAST instructionmodifies the namespace.

IMPORT_FROM(namei)¶

Loads the attributeco_names[namei] from the module found in TOS. Theresulting object is pushed onto the stack, to be subsequently stored by aSTORE_FAST instruction.

JUMP_FORWARD(delta)¶

Increments bytecode counter bydelta.

POP_JUMP_IF_TRUE(target)¶

If TOS is true, sets the bytecode counter totarget. TOS is popped.

New in version 3.1.

POP_JUMP_IF_FALSE(target)¶

If TOS is false, sets the bytecode counter totarget. TOS is popped.

New in version 3.1.

JUMP_IF_TRUE_OR_POP(target)¶

If TOS is true, sets the bytecode counter totarget and leaves TOS on thestack. Otherwise (TOS is false), TOS is popped.

New in version 3.1.

JUMP_IF_FALSE_OR_POP(target)¶

If TOS is false, sets the bytecode counter totarget and leaves TOS on thestack. Otherwise (TOS is true), TOS is popped.

New in version 3.1.

JUMP_ABSOLUTE(target)¶

Set bytecode counter totarget.

FOR_ITER(delta)¶

TOS is aniterator. Call its__next__() method. Ifthis yields a new value, push it on the stack (leaving the iterator belowit). If the iterator indicates it is exhausted TOS is popped, and the bytecode counter is incremented bydelta.

LOAD_GLOBAL(namei)¶

Loads the global namedco_names[namei] onto the stack.

SETUP_FINALLY(delta)¶

Pushes a try block from a try-finally or try-except clause onto the blockstack.delta points to the finally block or the first except block.

CALL_FINALLY(delta)¶

Pushes the address of the next instruction onto the stack and incrementsbytecode counter bydelta. Used for calling the finally block as a“subroutine”.

New in version 3.8.

LOAD_FAST(var_num)¶

Pushes a reference to the localco_varnames[var_num] onto the stack.

STORE_FAST(var_num)¶

Stores TOS into the localco_varnames[var_num].

DELETE_FAST(var_num)¶

Deletes localco_varnames[var_num].

LOAD_CLOSURE(i)¶

Pushes a reference to the cell contained in sloti of the cell and freevariable storage. The name of the variable isco_cellvars[i] ifi isless than the length ofco_cellvars. Otherwise it isco_freevars[i-len(co_cellvars)].

LOAD_DEREF(i)¶

Loads the cell contained in sloti of the cell and free variable storage.Pushes a reference to the object the cell contains on the stack.

LOAD_CLASSDEREF(i)¶

Much likeLOAD_DEREF but first checks the locals dictionary beforeconsulting the cell. This is used for loading free variables in classbodies.

New in version 3.4.

STORE_DEREF(i)¶

Stores TOS into the cell contained in sloti of the cell and free variablestorage.

DELETE_DEREF(i)¶

Empties the cell contained in sloti of the cell and free variable storage.Used by thedel statement.

New in version 3.2.

RAISE_VARARGS(argc)¶

Raises an exception using one of the 3 forms of theraise statement,depending on the value ofargc:

• 0:raise (re-raise previous exception)

• 1:raiseTOS (raise exception instance or type atTOS)

• 2:raiseTOS1fromTOS (raise exception instance or type atTOS1with__cause__ set toTOS)

CALL_FUNCTION(argc)¶

Calls a callable object with positional arguments.argc indicates the number of positional arguments.The top of the stack contains positional arguments, with the right-mostargument on top. Below the arguments is a callable object to call.CALL_FUNCTION pops all arguments and the callable object off the stack,calls the callable object with those arguments, and pushes the return valuereturned by the callable object.

Changed in version 3.6:This opcode is used only for calls with positional arguments.

CALL_FUNCTION_KW(argc)¶

Calls a callable object with positional (if any) and keyword arguments.argc indicates the total number of positional and keyword arguments.The top element on the stack contains a tuple of keyword argument names.Below that are keyword arguments in the order corresponding to the tuple.Below that are positional arguments, with the right-most parameter ontop. Below the arguments is a callable object to call.CALL_FUNCTION_KW pops all arguments and the callable object off the stack,calls the callable object with those arguments, and pushes the return valuereturned by the callable object.

Changed in version 3.6:Keyword arguments are packed in a tuple instead of a dictionary,argc indicates the total number of arguments.

CALL_FUNCTION_EX(flags)¶

Calls a callable object with variable set of positional and keywordarguments. If the lowest bit offlags is set, the top of the stackcontains a mapping object containing additional keyword arguments.Below that is an iterable object containing positional arguments anda callable object to call.BUILD_MAP_UNPACK_WITH_CALL andBUILD_TUPLE_UNPACK_WITH_CALL can be used for merging multiplemapping objects and iterables containing arguments.Before the callable is called, the mapping object and iterable objectare each “unpacked” and their contents passed in as keyword andpositional arguments respectively.CALL_FUNCTION_EX pops all arguments and the callable object off the stack,calls the callable object with those arguments, and pushes the return valuereturned by the callable object.

New in version 3.6.

LOAD_METHOD(namei)¶

Loads a method namedco_names[namei] from the TOS object. TOS is popped.This bytecode distinguishes two cases: if TOS has a method with the correctname, the bytecode pushes the unbound method and TOS. TOS will be used asthe first argument (self) byCALL_METHOD when calling theunbound method. Otherwise,NULL and the object return by the attributelookup are pushed.

New in version 3.7.

CALL_METHOD(argc)¶

Calls a method.argc is the number of positional arguments.Keyword arguments are not supported. This opcode is designed to be usedwithLOAD_METHOD. Positional arguments are on top of the stack.Below them, the two items described inLOAD_METHOD are on thestack (eitherself and an unbound method object orNULL and anarbitrary callable). All of them are popped and the return value is pushed.

New in version 3.7.

MAKE_FUNCTION(flags)¶

Pushes a new function object on the stack. From bottom to top, the consumedstack must consist of values if the argument carries a specified flag value

• 0x01 a tuple of default values for positional-only andpositional-or-keyword parameters in positional order

• 0x02 a dictionary of keyword-only parameters’ default values

• 0x04 an annotation dictionary

• 0x08 a tuple containing cells for free variables, making a closure

• the code associated with the function (at TOS1)

• thequalified name of the function (at TOS)

BUILD_SLICE(argc)¶

Pushes a slice object on the stack.argc must be 2 or 3. If it is 2,slice(TOS1,TOS) is pushed; if it is 3,slice(TOS2,TOS1,TOS) ispushed. See theslice() built-in function for more information.

EXTENDED_ARG(ext)¶

Prefixes any opcode which has an argument too big to fit into the default onebyte.ext holds an additional byte which act as higher bits in the argument.For each opcode, at most three prefixalEXTENDED_ARG are allowed, formingan argument from two-byte to four-byte.

FORMAT_VALUE(flags)¶

Used for implementing formatted literal strings (f-strings). Popsan optionalfmt_spec from the stack, then a requiredvalue.flags is interpreted as follows:

• (flags&0x03)==0x00:value is formatted as-is.

• (flags&0x03)==0x01: callstr() onvalue beforeformatting it.

• (flags&0x03)==0x02: callrepr() onvalue beforeformatting it.

• (flags&0x03)==0x03: callascii() onvalue beforeformatting it.

• (flags&0x04)==0x04: popfmt_spec from the stack and useit, else use an emptyfmt_spec.

Formatting is performed usingPyObject_Format(). Theresult is pushed on the stack.

New in version 3.6.

HAVE_ARGUMENT¶

This is not really an opcode. It identifies the dividing line betweenopcodes which don’t use their argument and those that do(<HAVE_ARGUMENT and>=HAVE_ARGUMENT, respectively).

Changed in version 3.6:Now every instruction has an argument, but opcodes<HAVE_ARGUMENTignore it. Before, only opcodes>=HAVE_ARGUMENT had an argument.

Opcode collections¶

These collections are provided for automatic introspection of bytecodeinstructions:

dis.opname¶

Sequence of operation names, indexable using the bytecode.

dis.opmap¶

Dictionary mapping operation names to bytecodes.

dis.cmp_op¶

Sequence of all compare operation names.

dis.hasconst¶

Sequence of bytecodes that access a constant.

dis.hasfree¶

Sequence of bytecodes that access a free variable (note that ‘free’ in thiscontext refers to names in the current scope that are referenced by innerscopes or names in outer scopes that are referenced from this scope. It doesnot include references to global or builtin scopes).

dis.hasname¶

Sequence of bytecodes that access an attribute by name.

dis.hasjrel¶

Sequence of bytecodes that have a relative jump target.

dis.hasjabs¶

Sequence of bytecodes that have an absolute jump target.

dis.haslocal¶

Sequence of bytecodes that access a local variable.

dis.hascompare¶

Sequence of bytecodes of Boolean operations.