py/objtype: Implement __delattr__ and __setattr__.

This patch implements support for class methods __delattr__ and __setattr__
for customising attribute access.  It is controlled by the config option
MICROPY_PY_DELATTR_SETATTR and is disabled by default.
This commit is contained in:
dmazzella 2017-01-03 11:00:12 +01:00 committed by Damien George
parent ec7dc7f8d7
commit 18e6569166
4 changed files with 104 additions and 0 deletions

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@ -635,6 +635,12 @@ typedef double mp_float_t;
#define MICROPY_PY_DESCRIPTORS (0)
#endif
// Whether to support class __delattr__ and __setattr__ methods
// This costs some code size and makes all del attrs and store attrs slow
#ifndef MICROPY_PY_DELATTR_SETATTR
#define MICROPY_PY_DELATTR_SETATTR (0)
#endif
// Support for async/await/async for/async with
#ifndef MICROPY_PY_ASYNC_AWAIT
#define MICROPY_PY_ASYNC_AWAIT (1)

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@ -533,6 +533,15 @@ STATIC void mp_obj_instance_load_attr(mp_obj_t self_in, qstr attr, mp_obj_t *des
// try __getattr__
if (attr != MP_QSTR___getattr__) {
#if MICROPY_PY_DELATTR_SETATTR
// If the requested attr is __setattr__/__delattr__ then don't delegate the lookup
// to __getattr__. If we followed CPython's behaviour then __setattr__/__delattr__
// would have already been found in the "object" base class.
if (attr == MP_QSTR___setattr__ || attr == MP_QSTR___delattr__) {
return;
}
#endif
mp_obj_t dest2[3];
mp_load_method_maybe(self_in, MP_QSTR___getattr__, dest2);
if (dest2[0] != MP_OBJ_NULL) {
@ -626,10 +635,35 @@ STATIC bool mp_obj_instance_store_attr(mp_obj_t self_in, qstr attr, mp_obj_t val
if (value == MP_OBJ_NULL) {
// delete attribute
#if MICROPY_PY_DELATTR_SETATTR
// try __delattr__ first
mp_obj_t attr_delattr_method[3];
mp_load_method_maybe(self_in, MP_QSTR___delattr__, attr_delattr_method);
if (attr_delattr_method[0] != MP_OBJ_NULL) {
// __delattr__ exists, so call it
attr_delattr_method[2] = MP_OBJ_NEW_QSTR(attr);
mp_call_method_n_kw(1, 0, attr_delattr_method);
return true;
}
#endif
mp_map_elem_t *elem = mp_map_lookup(&self->members, MP_OBJ_NEW_QSTR(attr), MP_MAP_LOOKUP_REMOVE_IF_FOUND);
return elem != NULL;
} else {
// store attribute
#if MICROPY_PY_DELATTR_SETATTR
// try __setattr__ first
mp_obj_t attr_setattr_method[4];
mp_load_method_maybe(self_in, MP_QSTR___setattr__, attr_setattr_method);
if (attr_setattr_method[0] != MP_OBJ_NULL) {
// __setattr__ exists, so call it
attr_setattr_method[2] = MP_OBJ_NEW_QSTR(attr);
attr_setattr_method[3] = value;
mp_call_method_n_kw(2, 0, attr_setattr_method);
return true;
}
#endif
mp_map_lookup(&self->members, MP_OBJ_NEW_QSTR(attr), MP_MAP_LOOKUP_ADD_IF_NOT_FOUND)->value = value;
return true;
}

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@ -0,0 +1,63 @@
# test __delattr__ and __setattr__
# feature test for __setattr__/__delattr__
try:
class Test():
def __delattr__(self, attr): pass
del Test().noexist
except AttributeError:
import sys
print('SKIP')
sys.exit()
# this class just prints the calls to see if they were executed
class A():
def __getattr__(self, attr):
print('get', attr)
return 1
def __setattr__(self, attr, val):
print('set', attr, val)
def __delattr__(self, attr):
print('del', attr)
a = A()
# check basic behaviour
print(getattr(a, 'foo'))
setattr(a, 'bar', 2)
delattr(a, 'baz')
# check meta behaviour
getattr(a, '__getattr__') # should not call A.__getattr__
getattr(a, '__setattr__') # should not call A.__getattr__
getattr(a, '__delattr__') # should not call A.__getattr__
setattr(a, '__setattr__', 1) # should call A.__setattr__
delattr(a, '__delattr__') # should call A.__delattr__
# this class acts like a dictionary
class B:
def __init__(self, d):
# store the dict in the class, not instance, so
# we don't get infinite recursion in __getattr_
B.d = d
def __getattr__(self, attr):
if attr in B.d:
return B.d[attr]
else:
raise AttributeError(attr)
def __setattr__(self, attr, value):
B.d[attr] = value
def __delattr__(self, attr):
del B.d[attr]
a = B({"a":1, "b":2})
print(a.a, a.b)
a.a = 3
print(a.a, a.b)
del a.a
try:
print(a.a)
except AttributeError:
print("AttributeError")

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@ -32,6 +32,7 @@
#include <mpconfigport.h>
#define MICROPY_PY_DELATTR_SETATTR (1)
#define MICROPY_PY_BUILTINS_HELP (1)
#define MICROPY_PY_BUILTINS_HELP_MODULES (1)
#define MICROPY_PY_URANDOM_EXTRA_FUNCS (1)