GNU Info
(python2.1-lib.info)Python Byte Code Instructions
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.
`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'.
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 / TOS'.
`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 <`'< TOS'.
`BINARY_RSHIFT'
Implements `TOS = TOS1 >`'> TOS'.
`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 / TOS'.
`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 <`'< TOS'.
`INPLACE_RSHIFT'
Implements in-place `TOS = TOS1 >`'> TOS'.
`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[:TOS1]'.
`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]'.
`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.
`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.
`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 with `None'.
`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
use `STORE_LOCAL' or `STORE_GLOBAL' if 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 subsequent `STORE_FAST' instruction
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 a `STORE_FAST' instruction.
`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_LOOP delta'
Iterate over a sequence. TOS is the current index, TOS1 the
sequence. First, the next element is computed. If the sequence
is exhausted, increment byte code counter by DELTA. Otherwise,
push the sequence, the incremented counter, and the current item
onto the stack.
`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 is `co_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'
Sets the current line number to LINENO.
`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 the `slice()' 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.
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