is there a feautre similar to C macros which lets you reuse code in an inline manner, without creating a seperate scope for that piece of code?
for example:
a=3
def foo():
a=4
foo()
print a
will print 3, however i want it to print 4.
i am aware of solutions involving objects like classes or a global dict, however i'm looking for a more primitive solution (like a function decorator for example) that would simply let me make changes inside the scope of the caller instead.
thank you very much
edit:any solution that requires declaring which variables i'm going to use OR declaring a "namespace" like mutabale objects beforehand is not a solution i'm looking for.
i had made an attempt on my own:
def pgame():
a=3
c=5
print locals()
game(a)
print locals()
class inline_func(object):
def __init__(self, f):
self.f = f
def __call__(self, *args, **kwargs):
return self.f(*args, **kwargs)
#to be @inline_func
def game(b, a=4):
exec("inspect.stack()[3][0].f_locals.update(inspect.stack()[1] [0].f_locals)\nctypes.pythonapi.PyFrame_LocalsToFast(ctypes.py_object(inspect.stack()[3][0]),ctypes.c_int(0))\ninspect.stack()[1][0].f_locals.update(inspect.stack()[3][0].f_locals)\nctypes.pythonapi.PyFrame_LocalsToFast(ctypes.py_object(inspect.stack()[1][0]),ctypes.c_int(0))")
try:
print "your code here"
finally:
exec("inspect.stack()[3][0].f_locals.update(inspect.stack()[1][0].f_locals)\nctypes.pythonapi.PyFrame_LocalsToFast(ctypes.py_object(inspect.stack()[3][0]),ctypes.c_int(0))")
@inline_func
def strip_game(b, a=4):
print "your code here"
but i have ran into a serious problem with how to inject code into strip_game without ruining the debugability of the program, because i had only thought of creating a new code object or using exec, both suffering from some severe problems.
MAJOR EDIT:
ok, so i have something close to a working solution, however i encounter a very wierd problem:
import inspect
import ctypes
import struct
import dis
import types
def cgame():
a=3
c=5
print locals()
strip_game(a)
print locals()
def pgame():
a=3
c=5
print locals()
game(a)
print locals()
class empty_deco(object):
def __init__(self, f):
self.f = f
def __call__(self, *args, **kwargs):
return self.f(*args, **kwargs)
debug_func = None
class inline_func(object):
def __init__(self, f):
self.f = f
def __call__(self, *args, **kwargs):
init_exec_string = "inspect.stack()[3][0].f_locals.update(inspect.stack()[1][0].f_locals)\n" + \
"ctypes.pythonapi.PyFrame_LocalsToFast(ctypes.py_object(inspect.stack()[3][0]),ctypes.c_int(0))\n" + \
"inspect.stack()[1][0].f_locals.update(inspect.stack()[3][0].f_locals)\n" + \
"ctypes.pythonapi.PyFrame_LocalsToFast(ctypes.py_object(inspect.stack()[1][0]),ctypes.c_int(0))"
fini_exec_string = "inspect.stack()[3][0].f_locals.update(inspect.stack()[1][0].f_locals)\n" + \
"ctypes.pythonapi.PyFrame_LocalsToFast(ctypes.py_object(inspect.stack()[3][0]),ctypes.c_int(0))"
co_stacksize = max(6, self.f.func_code.co_stacksize) # make sure we have enough space on the stack for everything
co_consts = self.f.func_code.co_consts +(init_exec_string, fini_exec_string)
init = "d" + struct.pack("H", len(strip_game.f.func_code.co_consts)) #LOAD_CONST init_exec_string
init += "d\x00\x00\x04U" # LOAD_CONST None, DUP_TOP, EXEC_STMT
init += "z" + struct.pack("H", len(self.f.func_code.co_code) + 4) #SETUP_FINALLY
fini = "Wd\x00\x00" # POP_BLOCK, LOAD_CONST None
fini += "d" + struct.pack("H", len(strip_game.f.func_code.co_consts) + 1) #LOAD_CONST fini_exec_string
fini += "d\x00\x00\x04UXd\x00\x00S" # LOAD_CONST None, DUP_TOP, EXEC_STMT, END_FINALLY, LOAD_CONST None, RETURN
co_code = init + self.f.func_code.co_code + fini
co_lnotab = "\x00\x00\x0b" + self.f.func_code.co_lnotab[1:] # every error in init will be attributed to @inline_func, errors in the function will be treated as expected, errors in fini will be attributed to the last line probably.
new_code = types.CodeType(
self.f.func_code.co_argcount,
self.f.func_code.co_nlocals,
co_stacksize,
self.f.func_code.co_flags & ~(1), # optimized functions are problematic for us
co_code,
co_consts,
self.f.func_code.co_names,
self.f.func_code.co_varnames,
self.f.func_code.co_filename,
self.f.func_code.co_name,
self.f.func_code.co_firstlineno,
co_lnotab,
self.f.func_code.co_freevars,
self.f.func_code.co_cellvars,)
self.inline_f = types.FunctionType(new_code, self.f.func_globals, self.f.func_name, self.f.func_defaults, self.f.func_closure)
#dis.dis(self.inline_f)
global debug_func
debug_func = self.inline_f
return self.inline_f(*args, **kwargs)
@empty_deco
def game(b, a=4):
exec("inspect.stack()[3][0].f_locals.update(inspect.stack()[1][0].f_locals)\nctypes.pythonapi.PyFrame_LocalsToFast(ctypes.py_object(inspect.stack()[3][0]),ctypes.c_int(0))\ninspect.stack()[1][0].f_locals.update(inspect.stack()[3][0].f_locals)\nctypes.pythonapi.PyFrame_LocalsToFast(ctypes.py_object(inspect.stack()[1][0]),ctypes.c_int(0))")
try:
print "inner locals:"
print locals()
print c
return None
finally:
exec("inspect.stack()[3][0].f_locals.update(inspect.stack()[1][0].f_locals)\nctypes.pythonapi.PyFrame_LocalsToFast(ctypes.py_object(inspect.stack()[3][0]),ctypes.c_int(0))")
@inline_func
def strip_game(b, a=4):
print "inner locals:"
print locals()
print c
return None
def stupid():
exec("print 'hello'")
try:
a=1
b=2
c=3
d=4
finally:
exec("print 'goodbye'")
now this seems to work however, i get the following:
>>>cgame()
{'a': 3, 'c': 5}
{'a': 4, 'c': 5, 'b': 3}
your code here
Traceback (most recent call last):
File "<pyshell#43>", line 1, in <module>
cgame()
File "C:\Python27\somefile.py", line 14, in cgame
strip_game(a)
File "C:\Python27\somefile.py", line 78, in __call__
return self.inline_f(*args, **kwargs)
File "C:\Python27\somefile.py", line 94, in strip_game
z = c
NameError: global name 'c' is not defined
now when i disassemble the functions, i get the following very wierd compilation difference between game and strip_game:
in game:
86 16 LOAD_NAME 0 (locals)
19 CALL_FUNCTION 0
22 PRINT_ITEM
23 PRINT_NEWLINE
87 24 **LOAD_NAME** 1 (c)
27 PRINT_ITEM
28 PRINT_NEWLINE
in strip game:
95 16 LOAD_GLOBAL 0 (locals)
19 CALL_FUNCTION 0
22 PRINT_ITEM
23 PRINT_NEWLINE
96 24 LOAD_GLOBAL 1 (c)
27 PRINT_ITEM
28 PRINT_NEWLINE
why is does this difference occur?
printstatement) - Nothing justifies it for beginners - just change your learning environment to use Python 3.8 - python 2 is only useful nowadays for legacy, very big projects, that can't be easily ported, and is otherwise dead) – Pericardium