Python dis.get_instructions() Examples

def get_instructions(co):
        code = co.co_code
        n = len(code)
        i = 0
        extended_arg = 0
        while i < n:
            offset = i
            c = code[i]
            op = ord(c)
            argval = None
            i = i + 1
            if op >= HAVE_ARGUMENT:
                oparg = ord(code[i]) + ord(code[i + 1]) * 256 + extended_arg
                extended_arg = 0
                i = i + 2
                if op == EXTENDED_ARG:
                    extended_arg = oparg * 65536

                if op in hasconst:
                    argval = co.co_consts[oparg]
            yield Instruction(offset, argval, opname[op]) 

def test_elim_jump_after_return1(self):
        # Eliminate dead code: jumps immediately after returns can't be reached
        def f(cond1, cond2):
            if cond1: return 1
            if cond2: return 2
            while 1:
                return 3
            while 1:
                if cond1: return 4
                return 5
            return 6
        self.assertNotInBytecode(f, 'JUMP_FORWARD')
        self.assertNotInBytecode(f, 'JUMP_ABSOLUTE')
        returns = [instr for instr in dis.get_instructions(f)
                          if instr.opname == 'RETURN_VALUE']
        self.assertEqual(len(returns), 6) 

def test_constant_folding(self):
        # Issue #11244: aggressive constant folding.
        exprs = [
            '3 * -5',
            '-3 * 5',
            '2 * (3 * 4)',
            '(2 * 3) * 4',
            '(-1, 2, 3)',
            '(1, -2, 3)',
            '(1, 2, -3)',
            '(1, 2, -3) * 6',
            'lambda x: x in {(3 * -5) + (-1 - 6), (1, -2, 3) * 2, None}',
        ]
        for e in exprs:
            code = compile(e, '', 'single')
            for instr in dis.get_instructions(code):
                self.assertFalse(instr.opname.startswith('UNARY_'))
                self.assertFalse(instr.opname.startswith('BINARY_'))
                self.assertFalse(instr.opname.startswith('BUILD_')) 

def test_elim_jump_after_return1(self):
        # Eliminate dead code: jumps immediately after returns can't be reached
        def f(cond1, cond2):
            if cond1: return 1
            if cond2: return 2
            while 1:
                return 3
            while 1:
                if cond1: return 4
                return 5
            return 6
        self.assertNotInBytecode(f, 'JUMP_FORWARD')
        self.assertNotInBytecode(f, 'JUMP_ABSOLUTE')
        returns = [instr for instr in dis.get_instructions(f)
                          if instr.opname == 'RETURN_VALUE']
        self.assertEqual(len(returns), 6) 

def test_constant_folding(self):
        # Issue #11244: aggressive constant folding.
        exprs = [
            '3 * -5',
            '-3 * 5',
            '2 * (3 * 4)',
            '(2 * 3) * 4',
            '(-1, 2, 3)',
            '(1, -2, 3)',
            '(1, 2, -3)',
            '(1, 2, -3) * 6',
            'lambda x: x in {(3 * -5) + (-1 - 6), (1, -2, 3) * 2, None}',
        ]
        for e in exprs:
            code = compile(e, '', 'single')
            for instr in dis.get_instructions(code):
                self.assertFalse(instr.opname.startswith('UNARY_'))
                self.assertFalse(instr.opname.startswith('BINARY_'))
                self.assertFalse(instr.opname.startswith('BUILD_')) 

def test_elim_jump_after_return1(self):
        # Eliminate dead code: jumps immediately after returns can't be reached
        def f(cond1, cond2):
            if cond1: return 1
            if cond2: return 2
            while 1:
                return 3
            while 1:
                if cond1: return 4
                return 5
            return 6
        self.assertNotInBytecode(f, 'JUMP_FORWARD')
        self.assertNotInBytecode(f, 'JUMP_ABSOLUTE')
        returns = [instr for instr in dis.get_instructions(f)
                          if instr.opname == 'RETURN_VALUE']
        self.assertEqual(len(returns), 6) 

def test_constant_folding(self):
        # Issue #11244: aggressive constant folding.
        exprs = [
            '3 * -5',
            '-3 * 5',
            '2 * (3 * 4)',
            '(2 * 3) * 4',
            '(-1, 2, 3)',
            '(1, -2, 3)',
            '(1, 2, -3)',
            '(1, 2, -3) * 6',
            'lambda x: x in {(3 * -5) + (-1 - 6), (1, -2, 3) * 2, None}',
        ]
        for e in exprs:
            code = compile(e, '', 'single')
            for instr in dis.get_instructions(code):
                self.assertFalse(instr.opname.startswith('UNARY_'))
                self.assertFalse(instr.opname.startswith('BINARY_'))
                self.assertFalse(instr.opname.startswith('BUILD_')) 

def co_code_findloadednames(co):
    """Find in the code of a code object, all loaded names.
    (by LOAD_NAME, LOAD_GLOBAL or LOAD_FAST) """

    import dis
    from opcode import HAVE_ARGUMENT, opmap
    hasloadname = (opmap['LOAD_NAME'],
                   opmap['LOAD_GLOBAL'], opmap['LOAD_FAST'])
    insns = dis.get_instructions(co)
    len_co_names = len(co.co_names)
    indexset = {}
    for insn in insns:
        if insn.opcode >= HAVE_ARGUMENT:
            if insn.opcode in hasloadname:
                indexset[insn.argval] = 1
                if len(indexset) >= len_co_names:
                    break
    for name in co.co_varnames:
        try:
            del indexset[name]
        except KeyError:
            pass
    return indexset 

def test_elim_jump_after_return1(self):
        # Eliminate dead code: jumps immediately after returns can't be reached
        def f(cond1, cond2):
            if cond1: return 1
            if cond2: return 2
            while 1:
                return 3
            while 1:
                if cond1: return 4
                return 5
            return 6
        self.assertNotInBytecode(f, 'JUMP_FORWARD')
        self.assertNotInBytecode(f, 'JUMP_ABSOLUTE')
        returns = [instr for instr in dis.get_instructions(f)
                          if instr.opname == 'RETURN_VALUE']
        self.assertEqual(len(returns), 6) 

def accessed_attributes_of_local(f, local_name):
        """
        Get a list of attributes of ``local_name`` accessed by ``f``.

        The analysis performed by this function is conservative, meaning that
        it's not guaranteed to find **all** attributes used.
        """
        try:
            instrs = dis.get_instructions(f)
        except TypeError:
            # Got a default wrapping an object that's not a python function. Be
            # conservative and assume this is safe.
            return set()

        used = set()
        # Find sequences of the form: LOAD_FAST(local_name), LOAD_ATTR(<name>).
        # This will find all usages of the form ``local_name.<name>``.
        #
        # It will **NOT** find usages in which ``local_name`` is aliased to
        # another name.
        for first, second in sliding_window(instrs, 2):
            if first.opname == "LOAD_FAST" and first.argval == local_name:
                if second.opname in ("LOAD_ATTR", "LOAD_METHOD", "STORE_ATTR"):
                    used.add(second.argval)
        return used 

def test_constant_folding(self):
        # Issue #11244: aggressive constant folding.
        exprs = [
            '3 * -5',
            '-3 * 5',
            '2 * (3 * 4)',
            '(2 * 3) * 4',
            '(-1, 2, 3)',
            '(1, -2, 3)',
            '(1, 2, -3)',
            '(1, 2, -3) * 6',
            'lambda x: x in {(3 * -5) + (-1 - 6), (1, -2, 3) * 2, None}',
        ]
        for e in exprs:
            code = compile(e, '', 'single')
            for instr in dis.get_instructions(code):
                self.assertFalse(instr.opname.startswith('UNARY_'))
                self.assertFalse(instr.opname.startswith('BINARY_'))
                self.assertFalse(instr.opname.startswith('BUILD_')) 

def test_folding_of_binops_on_constants(self):
        for line, elem in (
            ('a = 2+3+4', 9),                   # chained fold
            ('"@"*4', '@@@@'),                  # check string ops
            ('a="abc" + "def"', 'abcdef'),      # check string ops
            ('a = 3**4', 81),                   # binary power
            ('a = 3*4', 12),                    # binary multiply
            ('a = 13//4', 3),                   # binary floor divide
            ('a = 14%4', 2),                    # binary modulo
            ('a = 2+3', 5),                     # binary add
            ('a = 13-4', 9),                    # binary subtract
            ('a = (12,13)[1]', 13),             # binary subscr
            ('a = 13 << 2', 52),                # binary lshift
            ('a = 13 >> 2', 3),                 # binary rshift
            ('a = 13 & 7', 5),                  # binary and
            ('a = 13 ^ 7', 10),                 # binary xor
            ('a = 13 | 7', 15),                 # binary or
            ):
            code = compile(line, '', 'single')
            self.assertInBytecode(code, 'LOAD_CONST', elem)
            for instr in dis.get_instructions(code):
                self.assertFalse(instr.opname.startswith('BINARY_'))

        # Verify that unfoldables are skipped
        code = compile('a=2+"b"', '', 'single')
        self.assertInBytecode(code, 'LOAD_CONST', 2)
        self.assertInBytecode(code, 'LOAD_CONST', 'b')

        # Verify that large sequences do not result from folding
        code = compile('a="x"*10000', '', 'single')
        self.assertInBytecode(code, 'LOAD_CONST', 10000)
        self.assertNotIn("x"*10000, code.co_consts)
        code = compile('a=1<<1000', '', 'single')
        self.assertInBytecode(code, 'LOAD_CONST', 1000)
        self.assertNotIn(1<<1000, code.co_consts)
        code = compile('a=2**1000', '', 'single')
        self.assertInBytecode(code, 'LOAD_CONST', 1000)
        self.assertNotIn(2**1000, code.co_consts) 

def test_folding_of_unaryops_on_constants(self):
        for line, elem in (
            ('-0.5', -0.5),                     # unary negative
            ('-0.0', -0.0),                     # -0.0
            ('-(1.0-1.0)', -0.0),               # -0.0 after folding
            ('-0', 0),                          # -0
            ('~-2', 1),                         # unary invert
            ('+1', 1),                          # unary positive
        ):
            code = compile(line, '', 'single')
            self.assertInBytecode(code, 'LOAD_CONST', elem)
            for instr in dis.get_instructions(code):
                self.assertFalse(instr.opname.startswith('UNARY_'))

        # Check that -0.0 works after marshaling
        def negzero():
            return -(1.0-1.0)

        for instr in dis.get_instructions(code):
            self.assertFalse(instr.opname.startswith('UNARY_'))

        # Verify that unfoldables are skipped
        for line, elem, opname in (
            ('-"abc"', 'abc', 'UNARY_NEGATIVE'),
            ('~"abc"', 'abc', 'UNARY_INVERT'),
        ):
            code = compile(line, '', 'single')
            self.assertInBytecode(code, 'LOAD_CONST', elem)
            self.assertInBytecode(code, opname) 

def test_folding_of_tuples_of_constants(self):
        for line, elem in (
            ('a = 1,2,3', (1, 2, 3)),
            ('("a","b","c")', ('a', 'b', 'c')),
            ('a,b,c = 1,2,3', (1, 2, 3)),
            ('(None, 1, None)', (None, 1, None)),
            ('((1, 2), 3, 4)', ((1, 2), 3, 4)),
            ):
            code = compile(line,'','single')
            self.assertInBytecode(code, 'LOAD_CONST', elem)
            self.assertNotInBytecode(code, 'BUILD_TUPLE')

        # Long tuples should be folded too.
        code = compile(repr(tuple(range(10000))),'','single')
        self.assertNotInBytecode(code, 'BUILD_TUPLE')
        # One LOAD_CONST for the tuple, one for the None return value
        load_consts = [instr for instr in dis.get_instructions(code)
                              if instr.opname == 'LOAD_CONST']
        self.assertEqual(len(load_consts), 2)

        # Bug 1053819:  Tuple of constants misidentified when presented with:
        # . . . opcode_with_arg 100   unary_opcode   BUILD_TUPLE 1  . . .
        # The following would segfault upon compilation
        def crater():
            (~[
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
            ],) 

def test_elim_extra_return(self):
        # RETURN LOAD_CONST None RETURN  -->  RETURN
        def f(x):
            return x
        self.assertNotInBytecode(f, 'LOAD_CONST', None)
        returns = [instr for instr in dis.get_instructions(f)
                          if instr.opname == 'RETURN_VALUE']
        self.assertEqual(len(returns), 1) 

def test_elim_jump_after_return2(self):
        # Eliminate dead code: jumps immediately after returns can't be reached
        def f(cond1, cond2):
            while 1:
                if cond1: return 4
        self.assertNotInBytecode(f, 'JUMP_FORWARD')
        # There should be one jump for the while loop.
        returns = [instr for instr in dis.get_instructions(f)
                          if instr.opname == 'JUMP_ABSOLUTE']
        self.assertEqual(len(returns), 1)
        returns = [instr for instr in dis.get_instructions(f)
                          if instr.opname == 'RETURN_VALUE']
        self.assertEqual(len(returns), 2) 

def test_elim_extra_return(self):
        # RETURN LOAD_CONST None RETURN  -->  RETURN
        def f(x):
            return x
        self.assertNotInBytecode(f, 'LOAD_CONST', None)
        returns = [instr for instr in dis.get_instructions(f)
                          if instr.opname == 'RETURN_VALUE']
        self.assertEqual(len(returns), 1) 

def _walk_global_ops(code):
        """
        Yield (opcode, argument number) tuples for all
        global-referencing instructions in *code*.
        """
        for instr in dis.get_instructions(code):
            op = instr.opcode
            if op in GLOBAL_OPS:
                yield op, instr.arg 

def test_iteration(self):
        for obj in [_f, _C(1).__init__, "a=1", _f.__code__]:
            with self.subTest(obj=obj):
                via_object = list(dis.Bytecode(obj))
                via_generator = list(dis.get_instructions(obj))
                self.assertEqual(via_object, via_generator) 

def test_folding_of_unaryops_on_constants(self):
        for line, elem in (
            ('-0.5', -0.5),                     # unary negative
            ('-0.0', -0.0),                     # -0.0
            ('-(1.0-1.0)', -0.0),               # -0.0 after folding
            ('-0', 0),                          # -0
            ('~-2', 1),                         # unary invert
            ('+1', 1),                          # unary positive
        ):
            code = compile(line, '', 'single')
            self.assertInBytecode(code, 'LOAD_CONST', elem)
            for instr in dis.get_instructions(code):
                self.assertFalse(instr.opname.startswith('UNARY_'))

        # Check that -0.0 works after marshaling
        def negzero():
            return -(1.0-1.0)

        for instr in dis.get_instructions(code):
            self.assertFalse(instr.opname.startswith('UNARY_'))

        # Verify that unfoldables are skipped
        for line, elem, opname in (
            ('-"abc"', 'abc', 'UNARY_NEGATIVE'),
            ('~"abc"', 'abc', 'UNARY_INVERT'),
        ):
            code = compile(line, '', 'single')
            self.assertInBytecode(code, 'LOAD_CONST', elem)
            self.assertInBytecode(code, opname) 

def test_folding_of_binops_on_constants(self):
        for line, elem in (
            ('a = 2+3+4', 9),                   # chained fold
            ('"@"*4', '@@@@'),                  # check string ops
            ('a="abc" + "def"', 'abcdef'),      # check string ops
            ('a = 3**4', 81),                   # binary power
            ('a = 3*4', 12),                    # binary multiply
            ('a = 13//4', 3),                   # binary floor divide
            ('a = 14%4', 2),                    # binary modulo
            ('a = 2+3', 5),                     # binary add
            ('a = 13-4', 9),                    # binary subtract
            ('a = (12,13)[1]', 13),             # binary subscr
            ('a = 13 << 2', 52),                # binary lshift
            ('a = 13 >> 2', 3),                 # binary rshift
            ('a = 13 & 7', 5),                  # binary and
            ('a = 13 ^ 7', 10),                 # binary xor
            ('a = 13 | 7', 15),                 # binary or
            ):
            code = compile(line, '', 'single')
            self.assertInBytecode(code, 'LOAD_CONST', elem)
            for instr in dis.get_instructions(code):
                self.assertFalse(instr.opname.startswith('BINARY_'))

        # Verify that unfoldables are skipped
        code = compile('a=2+"b"', '', 'single')
        self.assertInBytecode(code, 'LOAD_CONST', 2)
        self.assertInBytecode(code, 'LOAD_CONST', 'b')

        # Verify that large sequences do not result from folding
        code = compile('a="x"*1000', '', 'single')
        self.assertInBytecode(code, 'LOAD_CONST', 1000) 

def test_folding_of_tuples_of_constants(self):
        for line, elem in (
            ('a = 1,2,3', (1, 2, 3)),
            ('("a","b","c")', ('a', 'b', 'c')),
            ('a,b,c = 1,2,3', (1, 2, 3)),
            ('(None, 1, None)', (None, 1, None)),
            ('((1, 2), 3, 4)', ((1, 2), 3, 4)),
            ):
            code = compile(line,'','single')
            self.assertInBytecode(code, 'LOAD_CONST', elem)
            self.assertNotInBytecode(code, 'BUILD_TUPLE')

        # Long tuples should be folded too.
        code = compile(repr(tuple(range(10000))),'','single')
        self.assertNotInBytecode(code, 'BUILD_TUPLE')
        # One LOAD_CONST for the tuple, one for the None return value
        load_consts = [instr for instr in dis.get_instructions(code)
                              if instr.opname == 'LOAD_CONST']
        self.assertEqual(len(load_consts), 2)

        # Bug 1053819:  Tuple of constants misidentified when presented with:
        # . . . opcode_with_arg 100   unary_opcode   BUILD_TUPLE 1  . . .
        # The following would segfault upon compilation
        def crater():
            (~[
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
            ],) 

def test_iteration(self):
        for obj in [_f, _C(1).__init__, "a=1", _f.__code__]:
            with self.subTest(obj=obj):
                via_object = list(dis.Bytecode(obj))
                via_generator = list(dis.get_instructions(obj))
                self.assertEqual(via_object, via_generator) 

def test_doubly_nested(self):
        with captured_stdout():
            inner = outer()()
        actual = dis.get_instructions(inner, first_line=expected_inner_line)
        self.assertEqual(list(actual), expected_opinfo_inner) 

def test_nested(self):
        with captured_stdout():
            f = outer()
        actual = dis.get_instructions(f, first_line=expected_f_line)
        self.assertEqual(list(actual), expected_opinfo_f) 

def test_outer(self):
        actual = dis.get_instructions(outer, first_line=expected_outer_line)
        self.assertEqual(list(actual), expected_opinfo_outer) 

def test_first_line_set_to_None(self):
        actual = dis.get_instructions(simple, first_line=None)
        self.assertEqual(list(actual), expected_opinfo_simple) 

def test_default_first_line(self):
        actual = dis.get_instructions(simple)
        self.assertEqual(list(actual), expected_opinfo_simple) 

def clean_instructions(self, code):
        return [
            inst
            for inst in get_instructions(code)
            if inst.opname != 'EXTENDED_ARG'
            if inst.lineno not in self.ignore_linenos
        ] 

def get_instructions(co):
    lineno = None
    for inst in _get_instructions(co):
        lineno = inst.starts_line or lineno
        assert_(lineno)
        inst.lineno = lineno
        yield inst