A nestedmodule decorator (Re: Namespaces are one honking great idea)
Gregory Ewing
greg.ewing at canterbury.ac.nz
Tue Jul 5 05:10:15 EDT 2016
Steven D'Aprano wrote:
> There's only so far I can go without support from the compiler.
It turns out one can go surprisingly far. Here's something I
cooked up that seems to meet almost all the requirements.
The only shortcoming I can think of is that a nestedmodule
inside another nestedmodule won't be able to see the names
in the outer nestedmodule directly (much like nested classes).
% python3 test_nestedmodule.py
0.7071067811865475
#------------------------------------------
#
# test_nestedmodule.py
#
#------------------------------------------
from math import pi, sin
from nestedmodule import nestedmodule
def f(x):
return x**2
@nestedmodule
def test():
def g(x):
return f(x) * pi
def h(x):
return sin(g(x))
y = test.h(0.5)
print(y)
#------------------------------------------
#
# nestedmodule.py
#
#------------------------------------------
from types import CodeType, ModuleType
def hack_code(f):
"""Hack 'return locals()' onto the end of the bytecode of f."""
code1 = f.__code__
bytes1 = code1.co_code
names1 = code1.co_names
n = len(names1)
names2 = names1 + ('locals',)
bytes2 = bytes1[:-4] + bytes([116, n, 0, 131, 0, 0, 83])
code2 = CodeType(code1.co_argcount, code1.co_kwonlyargcount, code1.co_nlocals,
code1.co_stacksize, code1.co_flags, bytes2, code1.co_consts, names2,
code1.co_varnames, code1.co_filename, code1.co_name, code1.co_firstlineno,
code1.co_lnotab, code1.co_freevars, code1.co_cellvars)
return code2
def nestedmodule(f):
c = hack_code(f)
l = eval(c, f.__globals__)
m = ModuleType(f.__name__)
m.__dict__.update(l)
return m
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