"""Disassembler of Python byte code into mnemonics."""
from opcode import __all__ as _opcodes_all
__all__ = ["code_info", "dis", "disassemble", "distb", "disco",
"findlinestarts", "findlabels", "show_code",
"get_instructions", "Instruction", "Bytecode"] + _opcodes_all
_have_code = (types.MethodType, types.FunctionType, types.CodeType,
classmethod, staticmethod, type)
FORMAT_VALUE = opmap['FORMAT_VALUE']
FORMAT_VALUE_CONVERTERS = (
MAKE_FUNCTION = opmap['MAKE_FUNCTION']
MAKE_FUNCTION_FLAGS = ('defaults', 'kwdefaults', 'annotations', 'closure')
def _try_compile(source, name):
"""Attempts to compile the given source, first as an expression and
then as a statement if the first approach fails.
Utility function to accept strings in functions that otherwise
c = compile(source, name, 'eval')
c = compile(source, name, 'exec')
def dis(x=None, *, file=None, depth=None):
"""Disassemble classes, methods, functions, and other compiled objects.
With no argument, disassemble the last traceback.
Compiled objects currently include generator objects, async generator
objects, and coroutine objects, all of which store their code object
# Extract functions from methods.
if hasattr(x, '__func__'):
# Extract compiled code objects from...
if hasattr(x, '__code__'): # ...a function, or
elif hasattr(x, 'gi_code'): #...a generator object, or
elif hasattr(x, 'ag_code'): #...an asynchronous generator object, or
elif hasattr(x, 'cr_code'): #...a coroutine.
# Perform the disassembly.
if hasattr(x, '__dict__'): # Class or module
items = sorted(x.__dict__.items())
if isinstance(x1, _have_code):
print("Disassembly of %s:" % name, file=file)
dis(x1, file=file, depth=depth)
print("Sorry:", msg, file=file)
elif hasattr(x, 'co_code'): # Code object
_disassemble_recursive(x, file=file, depth=depth)
elif isinstance(x, (bytes, bytearray)): # Raw bytecode
_disassemble_bytes(x, file=file)
elif isinstance(x, str): # Source code
_disassemble_str(x, file=file, depth=depth)
raise TypeError("don't know how to disassemble %s objects" %
def distb(tb=None, *, file=None):
"""Disassemble a traceback (default: last traceback)."""
raise RuntimeError("no last traceback to disassemble") from None
while tb.tb_next: tb = tb.tb_next
disassemble(tb.tb_frame.f_code, tb.tb_lasti, file=file)
# The inspect module interrogates this dictionary to build its
# list of CO_* constants. It is also used by pretty_flags to
# turn the co_flags field into a human readable list.
256: "ITERABLE_COROUTINE",
"""Return pretty representation of code flags."""
names.append(COMPILER_FLAG_NAMES.get(flag, hex(flag)))
"""Helper to handle methods, compiled or raw code objects, and strings."""
# Extract functions from methods.
if hasattr(x, '__func__'):
# Extract compiled code objects from...
if hasattr(x, '__code__'): # ...a function, or
elif hasattr(x, 'gi_code'): #...a generator object, or
elif hasattr(x, 'ag_code'): #...an asynchronous generator object, or
elif hasattr(x, 'cr_code'): #...a coroutine.
x = _try_compile(x, "<disassembly>")
# By now, if we don't have a code object, we can't disassemble x.
if hasattr(x, 'co_code'):
raise TypeError("don't know how to disassemble %s objects" %
"""Formatted details of methods, functions, or code."""
return _format_code_info(_get_code_object(x))
def _format_code_info(co):
lines.append("Name: %s" % co.co_name)
lines.append("Filename: %s" % co.co_filename)
lines.append("Argument count: %s" % co.co_argcount)
lines.append("Positional-only arguments: %s" % co.co_posonlyargcount)
lines.append("Kw-only arguments: %s" % co.co_kwonlyargcount)
lines.append("Number of locals: %s" % co.co_nlocals)
lines.append("Stack size: %s" % co.co_stacksize)
lines.append("Flags: %s" % pretty_flags(co.co_flags))
lines.append("Constants:")
for i_c in enumerate(co.co_consts):
lines.append("%4d: %r" % i_c)
for i_n in enumerate(co.co_names):
lines.append("%4d: %s" % i_n)
lines.append("Variable names:")
for i_n in enumerate(co.co_varnames):
lines.append("%4d: %s" % i_n)
lines.append("Free variables:")
for i_n in enumerate(co.co_freevars):
lines.append("%4d: %s" % i_n)
lines.append("Cell variables:")
for i_n in enumerate(co.co_cellvars):
lines.append("%4d: %s" % i_n)
def show_code(co, *, file=None):
"""Print details of methods, functions, or code to *file*.
If *file* is not provided, the output is printed on stdout.
print(code_info(co), file=file)
_Instruction = collections.namedtuple("_Instruction",
"opname opcode arg argval argrepr offset starts_line is_jump_target")
_Instruction.opname.__doc__ = "Human readable name for operation"
_Instruction.opcode.__doc__ = "Numeric code for operation"
_Instruction.arg.__doc__ = "Numeric argument to operation (if any), otherwise None"
_Instruction.argval.__doc__ = "Resolved arg value (if known), otherwise same as arg"
_Instruction.argrepr.__doc__ = "Human readable description of operation argument"
_Instruction.offset.__doc__ = "Start index of operation within bytecode sequence"
_Instruction.starts_line.__doc__ = "Line started by this opcode (if any), otherwise None"
_Instruction.is_jump_target.__doc__ = "True if other code jumps to here, otherwise False"
class Instruction(_Instruction):
"""Details for a bytecode operation
opname - human readable name for operation
opcode - numeric code for operation
arg - numeric argument to operation (if any), otherwise None
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), otherwise None
is_jump_target - True if other code jumps to here, otherwise False
def _disassemble(self, lineno_width=3, mark_as_current=False, offset_width=4):
"""Format instruction details for inclusion in disassembly output
*lineno_width* sets the width of the line number field (0 omits it)
*mark_as_current* inserts a '-->' marker arrow as part of the line
*offset_width* sets the width of the instruction offset field
# Column: Source code line number
if self.starts_line is not None:
lineno_fmt = "%%%dd" % lineno_width
fields.append(lineno_fmt % self.starts_line)
fields.append(' ' * lineno_width)
# Column: Current instruction indicator
# Column: Jump target marker
# Column: Instruction offset from start of code sequence
fields.append(repr(self.offset).rjust(offset_width))
fields.append(self.opname.ljust(_OPNAME_WIDTH))
# Column: Opcode argument
fields.append(repr(self.arg).rjust(_OPARG_WIDTH))
# Column: Opcode argument details
fields.append('(' + self.argrepr + ')')
return ' '.join(fields).rstrip()
def get_instructions(x, *, first_line=None):
"""Iterator for the opcodes in methods, functions or code
Generates a series of Instruction named tuples giving the details of
each operations in the supplied code.
If *first_line* is not None, it indicates the line number that should
be reported for the first source line in the disassembled code.
Otherwise, the source line information (if any) is taken directly from
the disassembled code object.
cell_names = co.co_cellvars + co.co_freevars
linestarts = dict(findlinestarts(co))
if first_line is not None:
line_offset = first_line - co.co_firstlineno
return _get_instructions_bytes(co.co_code, co.co_varnames, co.co_names,
co.co_consts, cell_names, linestarts,
def _get_const_info(const_index, const_list):
"""Helper to get optional details about const references
Returns the dereferenced constant and its repr if the constant
Otherwise returns the constant index and its repr().
if const_list is not None:
argval = const_list[const_index]
return argval, repr(argval)
def _get_name_info(name_index, name_list):
"""Helper to get optional details about named references
Returns the dereferenced name as both value and repr if the name
Otherwise returns the name index and its repr().
if name_list is not None:
argval = name_list[name_index]
def _get_instructions_bytes(code, varnames=None, names=None, constants=None,
cells=None, linestarts=None, line_offset=0):
"""Iterate over the instructions in a bytecode string.
Generates a sequence of Instruction namedtuples giving the details of each
opcode. Additional information about the code's runtime environment
(e.g. variable names, constants) can be specified using optional
labels = findlabels(code)
for offset, op, arg in _unpack_opargs(code):
if linestarts is not None:
starts_line = linestarts.get(offset, None)
if starts_line is not None:
starts_line += line_offset
is_jump_target = offset in labels
# Set argval to the dereferenced value of the argument when
# available, and argrepr to the string representation of argval.
# _disassemble_bytes needs the string repr of the
# raw name index for LOAD_GLOBAL, LOAD_CONST, etc.
argval, argrepr = _get_const_info(arg, constants)
argval, argrepr = _get_name_info(arg, names)
argval = offset + 2 + arg
argrepr = "to " + repr(argval)
argval, argrepr = _get_name_info(arg, varnames)
argval, argrepr = _get_name_info(arg, cells)
argval, argrepr = FORMAT_VALUE_CONVERTERS[arg & 0x3]
argval = (argval, bool(arg & 0x4))
elif op == MAKE_FUNCTION:
argrepr = ', '.join(s for i, s in enumerate(MAKE_FUNCTION_FLAGS)
yield Instruction(opname[op], op,
offset, starts_line, is_jump_target)
def disassemble(co, lasti=-1, *, file=None):
"""Disassemble a code object."""
cell_names = co.co_cellvars + co.co_freevars
linestarts = dict(findlinestarts(co))
_disassemble_bytes(co.co_code, lasti, co.co_varnames, co.co_names,
co.co_consts, cell_names, linestarts, file=file)
def _disassemble_recursive(co, *, file=None, depth=None):
disassemble(co, file=file)
if depth is None or depth > 0:
if hasattr(x, 'co_code'):
print("Disassembly of %r:" % (x,), file=file)
_disassemble_recursive(x, file=file, depth=depth)
def _disassemble_bytes(code, lasti=-1, varnames=None, names=None,
constants=None, cells=None, linestarts=None,
*, file=None, line_offset=0):
# Omit the line number column entirely if we have no line number info
show_lineno = linestarts is not None
maxlineno = max(linestarts.values()) + line_offset
lineno_width = len(str(maxlineno))
maxoffset = len(code) - 2
offset_width = len(str(maxoffset))
for instr in _get_instructions_bytes(code, varnames, names,
constants, cells, linestarts,
line_offset=line_offset):
new_source_line = (show_lineno and
instr.starts_line is not None and
is_current_instr = instr.offset == lasti
print(instr._disassemble(lineno_width, is_current_instr, offset_width),
def _disassemble_str(source, **kwargs):
"""Compile the source string, then disassemble the code object."""
_disassemble_recursive(_try_compile(source, '<dis>'), **kwargs)
disco = disassemble # XXX For backwards compatibility
def _unpack_opargs(code):
for i in range(0, len(code), 2):
arg = code[i+1] | extended_arg
extended_arg = (arg << 8) if op == EXTENDED_ARG else 0
"""Detect all offsets in a byte code which are jump targets.
Return the list of offsets.
for offset, op, arg in _unpack_opargs(code):
def findlinestarts(code):
"""Find the offsets in a byte code which are start of lines in the source.
Generate pairs (offset, lineno) as described in Python/compile.c.
byte_increments = code.co_lnotab[0::2]
line_increments = code.co_lnotab[1::2]
bytecode_len = len(code.co_code)
lineno = code.co_firstlineno
for byte_incr, line_incr in zip(byte_increments, line_increments):
# The rest of the lnotab byte offsets are past the end of
# the bytecode, so the lines were optimized away.
# line_increments is an array of 8-bit signed integers
"""The bytecode operations of a piece of code
Instantiate this with a function, method, other compiled object, string of
code, or a code object (as returned by compile()).
Iterating over this yields the bytecode operations as Instruction instances.
def __init__(self, x, *, first_line=None, current_offset=None):
self.codeobj = co = _get_code_object(x)
self.first_line = co.co_firstlineno
self.first_line = first_line
self._line_offset = first_line - co.co_firstlineno
self._cell_names = co.co_cellvars + co.co_freevars
self._linestarts = dict(findlinestarts(co))
self._original_object = x
self.current_offset = current_offset
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