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dmazzelladpgeorge
dmazzella
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dpgeorge
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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.
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‎py/mpconfig.h‎

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

‎py/objtype.c‎

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

‎tests/basics/class_delattr_setattr.py‎

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

‎unix/mpconfigport_coverage.h‎

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

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