18.10.1 Python Byte Code Instructions
The Python compiler currently generates the following byte code
instructions.
- STOP_CODE
- 
Indicates end-of-code to the compiler, not used by the interpreter.
- 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 position three.
- ROT_FOUR
- 
Lifts second, third and forth stack item one position up, moves top down to
position four.
- DUP_TOP
- 
Duplicates the reference on top of the stack.
Unary Operations take the top of the stack, apply the operation, and
push the result back on the stack.
- UNARY_POSITIVE
- 
Implements TOS = +TOS.
- UNARY_NEGATIVE
- 
Implements TOS = -TOS.
- UNARY_NOT
- 
Implements TOS = not TOS.
- UNARY_CONVERT
- 
Implements TOS = `TOS`.
- UNARY_INVERT
- 
Implements TOS = ~TOS.
- GET_ITER
- 
Implements TOS = iter(TOS).
Binary operations remove the top of the stack (TOS) and the second top-most
stack item (TOS1) from the stack.  They perform the operation, and put the
result back on the stack.
- BINARY_POWER
- 
Implements TOS = TOS1 ** TOS.
- BINARY_MULTIPLY
- 
Implements TOS = TOS1 * TOS.
- BINARY_DIVIDE
- 
Implements TOS = TOS1 / TOSwhenfrom __future__ import divisionis not in effect.
- BINARY_FLOOR_DIVIDE
- 
Implements TOS = TOS1 // TOS.
- BINARY_TRUE_DIVIDE
- 
Implements TOS = TOS1 / TOSwhenfrom __future__ import divisionis in effect.
- BINARY_MODULO
- 
Implements TOS = TOS1 % TOS.
- BINARY_ADD
- 
Implements TOS = TOS1 + TOS.
- BINARY_SUBTRACT
- 
Implements TOS = TOS1 - TOS.
- BINARY_SUBSCR
- 
Implements TOS = TOS1[TOS].
- BINARY_LSHIFT
- 
Implements TOS = TOS1 <.
- BINARY_RSHIFT
- 
Implements TOS = TOS1 >.
- BINARY_AND
- 
Implements TOS = TOS1 & TOS.
- BINARY_XOR
- 
Implements TOS = TOS1 ^ TOS.
- BINARY_OR
- 
Implements TOS = TOS1 | TOS.
In-place operations are like binary operations, in that they remove TOS and
TOS1, and push the result back on the stack, but the operation is done
in-place when TOS1 supports it, and the resulting TOS may be (but does not
have to be) the original TOS1.
- INPLACE_POWER
- 
Implements in-place TOS = TOS1 ** TOS.
- INPLACE_MULTIPLY
- 
Implements in-place TOS = TOS1 * TOS.
- INPLACE_DIVIDE
- 
Implements in-place TOS = TOS1 / TOSwhenfrom __future__ import divisionis not in effect.
- INPLACE_FLOOR_DIVIDE
- 
Implements in-place TOS = TOS1 // TOS.
- INPLACE_TRUE_DIVIDE
- 
Implements in-place TOS = TOS1 / TOSwhenfrom __future__ import divisionis in effect.
- INPLACE_MODULO
- 
Implements in-place TOS = TOS1 % TOS.
- INPLACE_ADD
- 
Implements in-place TOS = TOS1 + TOS.
- INPLACE_SUBTRACT
- 
Implements in-place TOS = TOS1 - TOS.
- INPLACE_LSHIFT
- 
Implements in-place TOS = TOS1 <.
- INPLACE_RSHIFT
- 
Implements in-place TOS = TOS1 >.
- INPLACE_AND
- 
Implements in-place TOS = TOS1 & TOS.
- INPLACE_XOR
- 
Implements in-place TOS = TOS1 ^ TOS.
- INPLACE_OR
- 
Implements in-place TOS = TOS1 | TOS.
The slice opcodes take up to three parameters.
- SLICE+0
- 
Implements TOS = TOS[:].
- SLICE+1
- 
Implements TOS = TOS1[TOS:].
- SLICE+2
- 
Implements TOS = TOS1[:TOS].
- SLICE+3
- 
Implements TOS = TOS2[TOS1:TOS].
Slice assignment needs even an additional parameter.  As any statement,
they put nothing on the stack.
- STORE_SLICE+0
- 
Implements TOS[:] = TOS1.
- STORE_SLICE+1
- 
Implements TOS1[TOS:] = TOS2.
- STORE_SLICE+2
- 
Implements TOS1[:TOS] = TOS2.
- STORE_SLICE+3
- 
Implements TOS2[TOS1:TOS] = TOS3.
- DELETE_SLICE+0
- 
Implements del TOS[:].
- DELETE_SLICE+1
- 
Implements del TOS1[TOS:].
- DELETE_SLICE+2
- 
Implements del TOS1[:TOS].
- DELETE_SLICE+3
- 
Implements del TOS2[TOS1:TOS].
- STORE_SUBSCR
- 
Implements TOS1[TOS] = TOS2.
- DELETE_SUBSCR
- 
Implements del TOS1[TOS].
Miscellaneous opcodes.
- PRINT_EXPR
- 
Implements the expression statement for the interactive mode.  TOS is
removed from the stack and printed.  In non-interactive mode, an
expression statement is terminated with POP_STACK.
- PRINT_ITEM
- 
Prints TOS to the file-like object bound to sys.stdout.  There
is one such instruction for each item in the print statement.
- PRINT_ITEM_TO
- 
Like PRINT_ITEM, but prints the item second from TOS to the
file-like object at TOS.  This is used by the extended print statement.
- PRINT_NEWLINE
- 
Prints a new line on sys.stdout.  This is generated as the
last operation of a print statement, unless the statement
ends with a comma.
- PRINT_NEWLINE_TO
- 
Like PRINT_NEWLINE, but prints the new line on the file-like
object on the TOS.  This is used by the extended print statement.
- BREAK_LOOP
- 
Terminates a loop due to a break statement.
- CONTINUE_LOOP    target
- 
Continues a loop due to a continue statement.  target
is the address to jump to (which should be a FOR_ITERinstruction).
- LIST_APPEND
- 
Calls list.append(TOS1, TOS).  Used to implement list comprehensions.
- LOAD_LOCALS
- 
Pushes a reference to the locals of the current scope on the stack.
This is used in the code for a class definition: After the class body
is evaluated, the locals are passed to the class definition.
- RETURN_VALUE
- 
Returns with TOS to the caller of the function.
- YIELD_VALUE
- 
Pops TOSand yields it from a generator.
- IMPORT_STAR
- 
Loads all symbols not starting with "_" directly from the module TOS
to the local namespace. The module is popped after loading all names.
This opcode implements from module import *.
- EXEC_STMT
- 
Implements exec TOS2,TOS1,TOS.  The compiler fills
missing optional parameters withNone.
- POP_BLOCK
- 
Removes one block from the block stack.  Per frame, there is a 
stack of blocks, denoting nested loops, try statements, and such.
- END_FINALLY
- 
Terminates a finally clause.  The interpreter recalls
whether the exception has to be re-raised, or whether the function
returns, and continues with the outer-next block.
- BUILD_CLASS
- 
Creates a new class object.  TOS is the methods dictionary, TOS1
the tuple of the names of the base classes, and TOS2 the class name.
All of the following opcodes expect arguments.  An argument is two
bytes, with the more significant byte last.
- STORE_NAME    namei
- 
Implements name = TOS. namei is the index of name
in the attribute co_names of the code object.
The compiler tries to useSTORE_LOCALorSTORE_GLOBALif possible.
- DELETE_NAME    namei
- 
Implements del name, where namei is the index into
co_names attribute of the code object.
- UNPACK_SEQUENCE    count
- 
Unpacks TOS into count individual values, which are put onto
the stack right-to-left.
- DUP_TOPX    count
- 
Duplicate count items, keeping them in the same order. Due to
implementation limits, count should be between 1 and 5 inclusive.
- STORE_ATTR    namei
- 
Implements TOS.name = TOS1, where namei is the index
of name in co_names.
- DELETE_ATTR    namei
- 
Implements del TOS.name, using namei as index into
co_names.
- STORE_GLOBAL    namei
- 
Works as STORE_NAME, but stores the name as a global.
- DELETE_GLOBAL    namei
- 
Works as DELETE_NAME, but deletes a global name.
- LOAD_CONST    consti
- 
Pushes "co_consts[consti]" onto the stack.
- LOAD_NAME    namei
- 
Pushes the value associated with "co_names[namei]" onto the stack.
- BUILD_TUPLE    count
- 
Creates a tuple consuming count items from the stack, and pushes
the resulting tuple onto the stack.
- BUILD_LIST    count
- 
Works as BUILD_TUPLE, but creates a list.
- BUILD_MAP    zero
- 
Pushes a new empty dictionary object onto the stack.  The argument is
ignored and set to zero by the compiler.
- LOAD_ATTR    namei
- 
Replaces TOS with getattr(TOS, co_names[namei]).
- COMPARE_OP    opname
- 
Performs a Boolean operation.  The operation name can be found
in cmp_op[opname].
- IMPORT_NAME    namei
- 
Imports the module co_names[namei].  The module object is
pushed onto the stack.  The current namespace is not affected: for a
proper import statement, a subsequentSTORE_FASTinstruction
modifies the namespace.
- IMPORT_FROM    namei
- 
Loads the attribute co_names[namei]from the module found in
TOS. The resulting object is pushed onto the stack, to be subsequently
stored by aSTORE_FASTinstruction.
- JUMP_FORWARD    delta
- 
Increments byte code counter by delta.
- JUMP_IF_TRUE    delta
- 
If TOS is true, increment the byte code counter by delta.  TOS is
left on the stack.
- JUMP_IF_FALSE    delta
- 
If TOS is false, increment the byte code counter by delta.  TOS
is not changed. 
- JUMP_ABSOLUTE    target
- 
Set byte code counter to target.
- FOR_ITER    delta
- 
TOSis an iterator.  Call its next() method.  If this
yields a new value, push it on the stack (leaving the iterator below
it).  If the iterator indicates it is exhaustedTOSis
popped, and the byte code counter is incremented by delta.
- LOAD_GLOBAL    namei
- 
Loads the global named co_names[namei]onto the stack.
- SETUP_LOOP    delta
- 
Pushes a block for a loop onto the block stack.  The block spans
from the current instruction with a size of delta bytes.
- SETUP_EXCEPT    delta
- 
Pushes a try block from a try-except clause onto the block stack.
delta points to the first except block.
- SETUP_FINALLY    delta
- 
Pushes a try block from a try-except clause onto the block stack.
delta points to the finally block.
- LOAD_FAST    var_num
- 
Pushes a reference to the local co_varnames[var_num]onto
the stack.
- STORE_FAST    var_num
- 
Stores TOS into the local co_varnames[var_num].
- DELETE_FAST    var_num
- 
Deletes local co_varnames[var_num].
- LOAD_CLOSURE    i
- 
Pushes a reference to the cell contained in slot i of the
cell and free variable storage.  The name of the variable is 
co_cellvars[i]if i is less than the length of
co_cellvars.  Otherwise it isco_freevars[i - len(co_cellvars)].
- LOAD_DEREF    i
- 
Loads the cell contained in slot i of the cell and free variable
storage.  Pushes a reference to the object the cell contains on the
stack. 
- STORE_DEREF    i
- 
Stores TOS into the cell contained in slot i of the cell and
free variable storage.
- SET_LINENO    lineno
- 
This opcode is obsolete.
- RAISE_VARARGS    argc
- 
Raises an exception. argc indicates the number of parameters
to the raise statement, ranging from 0 to 3.  The handler will find
the traceback as TOS2, the parameter as TOS1, and the exception
as TOS.
- CALL_FUNCTION    argc
- 
Calls a function.  The low byte of argc indicates the number of
positional parameters, the high byte the number of keyword parameters.
On the stack, the opcode finds the keyword parameters first.  For each
keyword argument, the value is on top of the key.  Below the keyword
parameters, the positional parameters are on the stack, with the
right-most parameter on top.  Below the parameters, the function object
to call is on the stack.
- MAKE_FUNCTION    argc
- 
Pushes a new function object on the stack.  TOS is the code associated
with the function.  The function object is defined to have argc
default parameters, which are found below TOS.
- MAKE_CLOSURE    argc
- 
Creates a new function object, sets its func_closure slot, and
pushes it on the stack.  TOS is the code associated with the function.
If the code object has N free variables, the next N items on the stack
are the cells for these variables.  The function also has argc
default parameters, where are found before the cells.
- 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)is pushed.
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 two bytes.  ext holds two additional bytes which, taken
together with the subsequent opcode's argument, comprise a four-byte
argument, ext being the two most-significant bytes.
- CALL_FUNCTION_VAR    argc
- 
Calls a function. argc is interpreted as in CALL_FUNCTION.
The top element on the stack contains the variable argument list, followed
by keyword and positional arguments.
- CALL_FUNCTION_KW    argc
- 
Calls a function. argc is interpreted as in CALL_FUNCTION.
The top element on the stack contains the keyword arguments dictionary, 
followed by explicit keyword and positional arguments.
- CALL_FUNCTION_VAR_KW    argc
- 
Calls a function. argc is interpreted as in
CALL_FUNCTION.  The top element on the stack contains the
keyword arguments dictionary, followed by the variable-arguments
tuple, followed by explicit keyword and positional arguments.
Release 2.4.4, documentation updated on 18 October 2006.
 
See About this document... for information on suggesting changes.