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_drafts/python-object-replacement.md
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| @@ -44,7 +44,7 @@ a = [1, 2, 3, 4] | |||||
| ...we are creating a list object with four integers, and binding it to the name | ...we are creating a list object with four integers, and binding it to the name | ||||
| `a`. In graph form:<sup><a id="ref2" href="#fn2">[2]</a></sup> | `a`. In graph form:<sup><a id="ref2" href="#fn2">[2]</a></sup> | ||||
| <svg width="223pt" height="44pt" viewBox="0.00 0.00 223.01 44.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 40)"><title>%3</title><polygon fill="white" stroke="none" points="-4,4 -4,-40 219.012,-40 219.012,4 -4,4"/><g id="node1" class="node"><title>L</title><polygon fill="none" stroke="black" stroke-width="0.5" points="215.018,-36 126.994,-36 126.994,-0 215.018,-0 215.018,-36"/><text text-anchor="middle" x="171.006" y="-15" font-family="Courier,monospace" font-size="10.00">[1, 2, 3, 4]</text></g><g id="node2" class="node"><title>a</title><ellipse fill="none" stroke="black" stroke-width="0.5" cx="27" cy="-18" rx="27" ry="18"/><text text-anchor="middle" x="27" y="-13.8" font-family="Courier,monospace" font-size="14.00">a</text></g><g id="edge1" class="edge"><title>a->L</title><path fill="none" stroke="black" stroke-width="0.5" d="M54.0461,-18C72.2389,-18 97.1211,-18 119.173,-18"/><polygon fill="black" stroke="black" stroke-width="0.5" points="119.339,-20.6251 126.839,-18 119.339,-15.3751 119.339,-20.6251"/></g></g></svg> | |||||
| <svg width="223pt" height="44pt" viewBox="0.00 0.00 223.01 44.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 40)"><polygon fill="white" stroke="none" points="-4,4 -4,-40 219.012,-40 219.012,4 -4,4"/><g id="node1" class="node"><title>L</title><polygon fill="none" stroke="black" stroke-width="0.5" points="215.018,-36 126.994,-36 126.994,-0 215.018,-0 215.018,-36"/><text text-anchor="middle" x="171.006" y="-15" font-family="Courier,monospace" font-size="10.00">[1, 2, 3, 4]</text></g><g id="node2" class="node"><title>a</title><ellipse fill="none" stroke="black" stroke-width="0.5" cx="27" cy="-18" rx="27" ry="18"/><text text-anchor="middle" x="27" y="-13.8" font-family="Courier,monospace" font-size="14.00">a</text></g><g id="edge1" class="edge"><title>a->L</title><path fill="none" stroke="black" stroke-width="0.5" d="M54.0461,-18C72.2389,-18 97.1211,-18 119.173,-18"/><polygon fill="black" stroke="black" stroke-width="0.5" points="119.339,-20.6251 126.839,-18 119.339,-15.3751 119.339,-20.6251"/></g></g></svg> | |||||
| In each of the following examples, we are creating new _references_ to the | In each of the following examples, we are creating new _references_ to the | ||||
| list object, but we are never duplicating it. Each reference points to the same | list object, but we are never duplicating it. Each reference points to the same | ||||
| @@ -74,7 +74,7 @@ d = wrapper(a) | |||||
| {% endhighlight %} | {% endhighlight %} | ||||
| <svg width="254pt" height="234pt" viewBox="0.00 0.00 253.96 234.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 238)"><title>%3</title><polygon fill="white" stroke="none" points="-4,4 -4,-238 249.96,-238 249.96,4 -4,4"/><g id="clust3" class="cluster"><title>cluster0</title><polygon fill="none" stroke="black" stroke-width="0.5" points="8,-8 8,-82 78,-82 78,-8 8,-8"/><text text-anchor="middle" x="43" y="-66.8" font-family="Courier,monospace" font-size="14.00">d</text></g><g id="node1" class="node"><title>obj</title><polygon fill="none" stroke="black" stroke-width="0.5" points="245.966,-153 157.943,-153 157.943,-117 245.966,-117 245.966,-153"/><text text-anchor="middle" x="201.954" y="-132" font-family="Courier,monospace" font-size="10.00">[1, 2, 3, 4]</text></g><g id="node2" class="node"><title>a</title><ellipse fill="none" stroke="black" stroke-width="0.5" cx="43" cy="-216" rx="27" ry="18"/><text text-anchor="middle" x="43" y="-211.8" font-family="Courier,monospace" font-size="14.00">a</text></g><g id="edge1" class="edge"><title>a->obj</title><path fill="none" stroke="black" stroke-width="0.5" d="M64.8423,-205.244C88.7975,-192.881 128.721,-172.278 159.152,-156.573"/><polygon fill="black" stroke="black" stroke-width="0.5" points="160.422,-158.872 165.883,-153.1 158.014,-154.206 160.422,-158.872"/></g><g id="node3" class="node"><title>b</title><ellipse fill="none" stroke="black" stroke-width="0.5" cx="43" cy="-162" rx="27" ry="18"/><text text-anchor="middle" x="43" y="-157.8" font-family="Courier,monospace" font-size="14.00">b</text></g><g id="edge2" class="edge"><title>b->obj</title><path fill="none" stroke="black" stroke-width="0.5" d="M69.2174,-157.662C90.9996,-153.915 123.147,-148.385 150.231,-143.726"/><polygon fill="black" stroke="black" stroke-width="0.5" points="150.777,-146.295 157.724,-142.437 149.887,-141.121 150.777,-146.295"/></g><g id="node4" class="node"><title>c</title><ellipse fill="none" stroke="black" stroke-width="0.5" cx="43" cy="-108" rx="41.897" ry="18"/><text text-anchor="middle" x="43" y="-103.8" font-family="Courier,monospace" font-size="14.00">c.data</text></g><g id="edge3" class="edge"><title>c->obj</title><path fill="none" stroke="black" stroke-width="0.5" d="M82.3954,-114.605C102.772,-118.11 128.077,-122.463 150.069,-126.247"/><polygon fill="black" stroke="black" stroke-width="0.5" points="149.86,-128.874 157.697,-127.559 150.75,-123.7 149.86,-128.874"/></g><g id="node5" class="node"><title>L</title><ellipse fill="none" stroke="black" stroke-width="0.5" cx="43" cy="-34" rx="27" ry="18"/><text text-anchor="middle" x="43" y="-29.8" font-family="Courier,monospace" font-size="14.00">L</text></g><g id="edge4" class="edge"><title>L->obj</title><path fill="none" stroke="black" stroke-width="0.5" d="M62.9324,-46.183C88.5083,-62.6411 134.554,-92.2712 166.386,-112.755"/><polygon fill="black" stroke="black" stroke-width="0.5" points="165.223,-115.128 172.951,-116.98 168.064,-110.714 165.223,-115.128"/></g></g></svg> | |||||
| <svg width="254pt" height="234pt" viewBox="0.00 0.00 253.96 234.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 238)"><polygon fill="white" stroke="none" points="-4,4 -4,-238 249.96,-238 249.96,4 -4,4"/><g id="clust3" class="cluster"><title>cluster0</title><polygon fill="none" stroke="black" stroke-width="0.5" points="8,-8 8,-82 78,-82 78,-8 8,-8"/><text text-anchor="middle" x="43" y="-66.8" font-family="Courier,monospace" font-size="14.00">d</text></g><g id="node1" class="node"><title>obj</title><polygon fill="none" stroke="black" stroke-width="0.5" points="245.966,-153 157.943,-153 157.943,-117 245.966,-117 245.966,-153"/><text text-anchor="middle" x="201.954" y="-132" font-family="Courier,monospace" font-size="10.00">[1, 2, 3, 4]</text></g><g id="node2" class="node"><title>a</title><ellipse fill="none" stroke="black" stroke-width="0.5" cx="43" cy="-216" rx="27" ry="18"/><text text-anchor="middle" x="43" y="-211.8" font-family="Courier,monospace" font-size="14.00">a</text></g><g id="edge1" class="edge"><title>a->obj</title><path fill="none" stroke="black" stroke-width="0.5" d="M64.8423,-205.244C88.7975,-192.881 128.721,-172.278 159.152,-156.573"/><polygon fill="black" stroke="black" stroke-width="0.5" points="160.422,-158.872 165.883,-153.1 158.014,-154.206 160.422,-158.872"/></g><g id="node3" class="node"><title>b</title><ellipse fill="none" stroke="black" stroke-width="0.5" cx="43" cy="-162" rx="27" ry="18"/><text text-anchor="middle" x="43" y="-157.8" font-family="Courier,monospace" font-size="14.00">b</text></g><g id="edge2" class="edge"><title>b->obj</title><path fill="none" stroke="black" stroke-width="0.5" d="M69.2174,-157.662C90.9996,-153.915 123.147,-148.385 150.231,-143.726"/><polygon fill="black" stroke="black" stroke-width="0.5" points="150.777,-146.295 157.724,-142.437 149.887,-141.121 150.777,-146.295"/></g><g id="node4" class="node"><title>c</title><ellipse fill="none" stroke="black" stroke-width="0.5" cx="43" cy="-108" rx="41.897" ry="18"/><text text-anchor="middle" x="43" y="-103.8" font-family="Courier,monospace" font-size="14.00">c.data</text></g><g id="edge3" class="edge"><title>c->obj</title><path fill="none" stroke="black" stroke-width="0.5" d="M82.3954,-114.605C102.772,-118.11 128.077,-122.463 150.069,-126.247"/><polygon fill="black" stroke="black" stroke-width="0.5" points="149.86,-128.874 157.697,-127.559 150.75,-123.7 149.86,-128.874"/></g><g id="node5" class="node"><title>L</title><ellipse fill="none" stroke="black" stroke-width="0.5" cx="43" cy="-34" rx="27" ry="18"/><text text-anchor="middle" x="43" y="-29.8" font-family="Courier,monospace" font-size="14.00">L</text></g><g id="edge4" class="edge"><title>L->obj</title><path fill="none" stroke="black" stroke-width="0.5" d="M62.9324,-46.183C88.5083,-62.6411 134.554,-92.2712 166.386,-112.755"/><polygon fill="black" stroke="black" stroke-width="0.5" points="165.223,-115.128 172.951,-116.98 168.064,-110.714 165.223,-115.128"/></g></g></svg> | |||||
| Note that these references are all equal. `a` is no more valid a name for the | Note that these references are all equal. `a` is no more valid a name for the | ||||
| list than `b`, `c.data`, or `L` (from the perspective of `d`, which is exposed | list than `b`, `c.data`, or `L` (from the perspective of `d`, which is exposed | ||||
| @@ -733,9 +733,9 @@ TypeError: readonly attribute | |||||
| Python clearly doesn't want us to re-bind bound methods, and a reasonable | Python clearly doesn't want us to re-bind bound methods, and a reasonable | ||||
| person would give up here, but we still have a few tricks up our sleeve. Let's | person would give up here, but we still have a few tricks up our sleeve. Let's | ||||
| examine the internal C structure of bound methods, | examine the internal C structure of bound methods, | ||||
| [`PyMethodObject`](https://github.com/python/cpython/blob/2.7/Include/classobject.h#L31). | |||||
| [`PyMethodObject`](https://github.com/python/cpython/blob/2.7/Include/classobject.h#L31): | |||||
| <svg width="559pt" height="200pt" viewBox="0.00 18.00 559.03 200.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 226)"><title>%3</title><polygon fill="white" stroke="none" points="-4,4 -4,-226 555.032,-226 555.032,4 -4,4"/><g id="clust2" class="cluster"><title>cluster</title><polygon fill="none" stroke="black" stroke-width="0" points="8,-8 8,-214 272,-214 272,-8 8,-8"/><text text-anchor="middle" x="140" y="-14.8" font-family="Courier,monospace" font-size="14.00">PyMethodObject</text></g><g id="node1" class="node"><title>obj</title><polygon fill="none" stroke="black" stroke-width="0.5" points="551.048,-110 336.984,-110 336.984,-74 551.048,-74 551.048,-110"/><text text-anchor="middle" x="444.016" y="-89" font-family="Courier,monospace" font-size="10.00"><__main__.A object at 0xdeadbeef></text></g><g id="node2" class="node"><title>struct</title><polygon fill="#eeeeee" stroke="none" points="24,-182 24,-202 256,-202 256,-182 24,-182"/><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-182 24,-202 256,-202 256,-182 24,-182"/><text text-anchor="start" x="27" y="-188.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">struct _object* </text><text text-anchor="start" x="161.422" y="-188.8" font-family="Courier,monospace" font-style="oblique" font-size="14.00" fill="#666666">_ob_next</text><polygon fill="#eeeeee" stroke="none" points="24,-162 24,-182 256,-182 256,-162 24,-162"/><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-162 24,-182 256,-182 256,-162 24,-162"/><text text-anchor="start" x="27" y="-168.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">struct _object* </text><text text-anchor="start" x="161.422" y="-168.8" font-family="Courier,monospace" font-style="oblique" font-size="14.00" fill="#666666">_ob_prev</text><polygon fill="#eeeeee" stroke="none" points="24,-142 24,-162 256,-162 256,-142 24,-142"/><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-142 24,-162 256,-162 256,-142 24,-142"/><text text-anchor="start" x="27" y="-148.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">Py_ssize_t </text><text text-anchor="start" x="119.415" y="-148.8" font-family="Courier,monospace" font-size="14.00">ob_refcnt</text><polygon fill="#eeeeee" stroke="none" points="24,-122 24,-142 256,-142 256,-122 24,-122"/><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-122 24,-142 256,-142 256,-122 24,-122"/><text text-anchor="start" x="26.5815" y="-128.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">struct _typeobject* </text><text text-anchor="start" x="194.609" y="-128.8" font-family="Courier,monospace" font-size="14.00">ob_type</text><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-102 24,-122 256,-122 256,-102 24,-102"/><text text-anchor="start" x="27" y="-108.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">PyObject* </text><text text-anchor="start" x="111.014" y="-108.8" font-family="Courier,monospace" font-size="14.00">im_func</text><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-82 24,-102 256,-102 256,-82 24,-82"/><text text-anchor="start" x="27" y="-88.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">PyObject* </text><text text-anchor="start" x="111.014" y="-88.8" font-family="Courier,monospace" font-size="14.00">im_self</text><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-62 24,-82 256,-82 256,-62 24,-62"/><text text-anchor="start" x="27" y="-68.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">PyObject* </text><text text-anchor="start" x="111.014" y="-68.8" font-family="Courier,monospace" font-size="14.00">im_class</text><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-42 24,-62 256,-62 256,-42 24,-42"/><text text-anchor="start" x="27" y="-48.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">PyObject* </text><text text-anchor="start" x="111.014" y="-48.8" font-family="Courier,monospace" font-size="14.00">im_weakreflist</text></g><g id="edge1" class="edge"><title>struct:f->obj</title><path fill="none" stroke="black" stroke-width="0.5" d="M257,-92C280.313,-92 305.269,-92 329.087,-92"/><polygon fill="black" stroke="black" stroke-width="0.5" points="329.277,-94.6251 336.777,-92 329.277,-89.3751 329.277,-94.6251"/></g></g></svg> | |||||
| <svg width="559pt" height="200pt" viewBox="0.00 18.00 559.03 200.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 226)"><polygon fill="white" stroke="none" points="-4,4 -4,-226 555.032,-226 555.032,4 -4,4"/><g id="clust2" class="cluster"><title>cluster</title><polygon fill="none" stroke="black" stroke-width="0" points="8,-8 8,-214 272,-214 272,-8 8,-8"/><text text-anchor="middle" x="140" y="-14.8" font-family="Courier,monospace" font-size="14.00">PyMethodObject</text></g><g id="node1" class="node"><title>obj</title><polygon fill="none" stroke="black" stroke-width="0.5" points="551.048,-110 336.984,-110 336.984,-74 551.048,-74 551.048,-110"/><text text-anchor="middle" x="444.016" y="-89" font-family="Courier,monospace" font-size="10.00"><__main__.A object at 0xdeadbeef></text></g><g id="node2" class="node"><title>struct</title><polygon fill="#eeeeee" stroke="none" points="24,-182 24,-202 256,-202 256,-182 24,-182"/><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-182 24,-202 256,-202 256,-182 24,-182"/><text text-anchor="start" x="27" y="-188.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">struct _object* </text><text text-anchor="start" x="161.422" y="-188.8" font-family="Courier,monospace" font-style="oblique" font-size="14.00" fill="#666666">_ob_next</text><polygon fill="#eeeeee" stroke="none" points="24,-162 24,-182 256,-182 256,-162 24,-162"/><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-162 24,-182 256,-182 256,-162 24,-162"/><text text-anchor="start" x="27" y="-168.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">struct _object* </text><text text-anchor="start" x="161.422" y="-168.8" font-family="Courier,monospace" font-style="oblique" font-size="14.00" fill="#666666">_ob_prev</text><polygon fill="#eeeeee" stroke="none" points="24,-142 24,-162 256,-162 256,-142 24,-142"/><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-142 24,-162 256,-162 256,-142 24,-142"/><text text-anchor="start" x="27" y="-148.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">Py_ssize_t </text><text text-anchor="start" x="119.415" y="-148.8" font-family="Courier,monospace" font-size="14.00">ob_refcnt</text><polygon fill="#eeeeee" stroke="none" points="24,-122 24,-142 256,-142 256,-122 24,-122"/><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-122 24,-142 256,-142 256,-122 24,-122"/><text text-anchor="start" x="26.5815" y="-128.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">struct _typeobject* </text><text text-anchor="start" x="194.609" y="-128.8" font-family="Courier,monospace" font-size="14.00">ob_type</text><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-102 24,-122 256,-122 256,-102 24,-102"/><text text-anchor="start" x="27" y="-108.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">PyObject* </text><text text-anchor="start" x="111.014" y="-108.8" font-family="Courier,monospace" font-size="14.00">im_func</text><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-82 24,-102 256,-102 256,-82 24,-82"/><text text-anchor="start" x="27" y="-88.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">PyObject* </text><text text-anchor="start" x="111.014" y="-88.8" font-family="Courier,monospace" font-size="14.00">im_self</text><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-62 24,-82 256,-82 256,-62 24,-62"/><text text-anchor="start" x="27" y="-68.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">PyObject* </text><text text-anchor="start" x="111.014" y="-68.8" font-family="Courier,monospace" font-size="14.00">im_class</text><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-42 24,-62 256,-62 256,-42 24,-42"/><text text-anchor="start" x="27" y="-48.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">PyObject* </text><text text-anchor="start" x="111.014" y="-48.8" font-family="Courier,monospace" font-size="14.00">im_weakreflist</text></g><g id="edge1" class="edge"><title>struct:f->obj</title><path fill="none" stroke="black" stroke-width="0.5" d="M257,-92C280.313,-92 305.269,-92 329.087,-92"/><polygon fill="black" stroke="black" stroke-width="0.5" points="329.277,-94.6251 336.777,-92 329.277,-89.3751 329.277,-94.6251"/></g></g></svg> | |||||
| The four gray fields of the struct come from | The four gray fields of the struct come from | ||||
| [`PyObject_HEAD`](https://github.com/python/cpython/blob/2.7/Include/object.h#L78), | [`PyObject_HEAD`](https://github.com/python/cpython/blob/2.7/Include/object.h#L78), | ||||
| @@ -790,6 +790,8 @@ Therefore, we can make our replacement like so: | |||||
| >>> offset = ptrs_in_struct * field_size + ctypes.sizeof(ctypes.c_ssize_t) | >>> offset = ptrs_in_struct * field_size + ctypes.sizeof(ctypes.c_ssize_t) | ||||
| >>> ctypes.memmove(id(f) + offset, ctypes.byref(ctypes.py_object(b)), field_size) | >>> ctypes.memmove(id(f) + offset, ctypes.byref(ctypes.py_object(b)), field_size) | ||||
| 4470258440 | 4470258440 | ||||
| >>> f.__self__ is b | |||||
| True | |||||
| >>> f() | >>> f() | ||||
| <__main__.B object at 0x10a8af290> | <__main__.B object at 0x10a8af290> | ||||
| @@ -797,7 +799,40 @@ Therefore, we can make our replacement like so: | |||||
| Excellent—it worked! | Excellent—it worked! | ||||
| [`PyCFunctionObject`](https://github.com/python/cpython/blob/2.7/Include/methodobject.h#L81) | |||||
| There's another kind of bound method, which is the built-in variety as opposed | |||||
| to the user-defined variety we saw above. An example is `a.__sizeof__()`: | |||||
| {% highlight pycon %} | |||||
| >>> a, b = A(), B() | |||||
| >>> f = a.__sizeof__ | |||||
| >>> f | |||||
| <built-in method __sizeof__ of A object at 0x10ab44b50> | |||||
| >>> replace(a, b) | |||||
| >>> f.__self__ | |||||
| <__main__.A object at 0x10ab44b50> | |||||
| {% endhighlight %} | |||||
| This is stored internally as a | |||||
| [`PyCFunctionObject`](https://github.com/python/cpython/blob/2.7/Include/methodobject.h#L81). | |||||
| Let's take a look at its layout: | |||||
| <svg width="559pt" height="180pt" viewBox="0.00 18.00 559.03 180.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 206)"><polygon fill="white" stroke="none" points="-4,4 -4,-206 555.032,-206 555.032,4 -4,4"/><g id="clust2" class="cluster"><title>cluster</title><polygon fill="none" stroke="black" stroke-width="0" points="8,-8 8,-194 272,-194 272,-8 8,-8"/><text text-anchor="middle" x="140" y="-14.8" font-family="Courier,monospace" font-size="14.00">PyCFunctionObject</text></g><g id="node1" class="node"><title>obj</title><polygon fill="none" stroke="black" stroke-width="0.5" points="551.048,-90 336.984,-90 336.984,-54 551.048,-54 551.048,-90"/><text text-anchor="middle" x="444.016" y="-69" font-family="Courier,monospace" font-size="10.00"><__main__.A object at 0xdeadbeef></text></g><g id="node2" class="node"><title>struct</title><polygon fill="#eeeeee" stroke="none" points="24,-162 24,-182 256,-182 256,-162 24,-162"/><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-162 24,-182 256,-182 256,-162 24,-162"/><text text-anchor="start" x="27" y="-168.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">struct _object* </text><text text-anchor="start" x="161.422" y="-168.8" font-family="Courier,monospace" font-style="oblique" font-size="14.00" fill="#666666">_ob_next</text><polygon fill="#eeeeee" stroke="none" points="24,-142 24,-162 256,-162 256,-142 24,-142"/><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-142 24,-162 256,-162 256,-142 24,-142"/><text text-anchor="start" x="27" y="-148.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">struct _object* </text><text text-anchor="start" x="161.422" y="-148.8" font-family="Courier,monospace" font-style="oblique" font-size="14.00" fill="#666666">_ob_prev</text><polygon fill="#eeeeee" stroke="none" points="24,-122 24,-142 256,-142 256,-122 24,-122"/><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-122 24,-142 256,-142 256,-122 24,-122"/><text text-anchor="start" x="27" y="-128.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">Py_ssize_t </text><text text-anchor="start" x="119.415" y="-128.8" font-family="Courier,monospace" font-size="14.00">ob_refcnt</text><polygon fill="#eeeeee" stroke="none" points="24,-102 24,-122 256,-122 256,-102 24,-102"/><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-102 24,-122 256,-122 256,-102 24,-102"/><text text-anchor="start" x="26.5815" y="-108.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">struct _typeobject* </text><text text-anchor="start" x="194.609" y="-108.8" font-family="Courier,monospace" font-size="14.00">ob_type</text><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-82 24,-102 256,-102 256,-82 24,-82"/><text text-anchor="start" x="27" y="-88.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">PyMethodDef* </text><text text-anchor="start" x="136.218" y="-88.8" font-family="Courier,monospace" font-size="14.00">m_ml</text><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-62 24,-82 256,-82 256,-62 24,-62"/><text text-anchor="start" x="27" y="-68.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">PyObject* </text><text text-anchor="start" x="111.014" y="-68.8" font-family="Courier,monospace" font-size="14.00">m_self</text><polygon fill="none" stroke="black" stroke-width="0.5" points="24,-42 24,-62 256,-62 256,-42 24,-42"/><text text-anchor="start" x="27" y="-48.8" font-family="Courier,monospace" font-size="14.00" fill="#888888">PyObject* </text><text text-anchor="start" x="111.014" y="-48.8" font-family="Courier,monospace" font-size="14.00">m_module</text></g><g id="edge1" class="edge"><title>struct:f->obj</title><path fill="none" stroke="black" stroke-width="0.5" d="M257,-72C280.313,-72 305.269,-72 329.087,-72"/><polygon fill="black" stroke="black" stroke-width="0.5" points="329.277,-74.6251 336.777,-72 329.277,-69.3751 329.277,-74.6251"/></g></g></svg> | |||||
| Fortunately, `m_self` here has the same offset as `im_self` from before, so we | |||||
| can just use the same code: | |||||
| {% highlight pycon %} | |||||
| >>> ctypes.memmove(id(f) + offset, ctypes.byref(ctypes.py_object(b)), field_size) | |||||
| 4474703768 | |||||
| >>> f.__self__ is b | |||||
| True | |||||
| >>> f | |||||
| <built-in method __sizeof__ of B object at 0x10ab4f150> | |||||
| {% endhighlight %} | |||||
| ### Dictionary keys | ### Dictionary keys | ||||