typedef struct { PyObject_VAR_HEAD /* Vector of pointers to list elements. list[0] is ob_item[0], etc. */ PyObject **ob_item;  /* ob_item contains space for 'allocated' elements. The number * currently in use is ob_size. * Invariants: * 0 <= ob_size <= allocated * len(list) == ob_size * ob_item == NULL implies ob_size == allocated == 0 * list.sort() temporarily sets allocated to -1 to detect mutations. * * Items must normally not be NULL, except during construction when * the list is not yet visible outside the function that builds it. */ Py_ssize_t allocated;} PyListObject;

/* PyDict_MINSIZE is the minimum size of a dictionary. This many slots are * allocated directly in the dict object (in the ma_smalltable member). * It must be a power of 2, and at least 4. 8 allows dicts with no more * than 5 active entries to live in ma_smalltable (and so avoid an * additional malloc); instrumentation suggested this suffices for the * majority of dicts (consisting mostly of usually-small instance dicts and * usually-small dicts created to pass keyword arguments). */#define PyDict_MINSIZE 8 typedef struct { /* Cached hash code of me_key. Note that hash codes are C longs. * We have to use Py_ssize_t instead because dict_popitem() abuses * me_hash to hold a search finger. */ Py_ssize_t me_hash; PyObject *me_key; PyObject *me_value;} PyDictEntry; /*To ensure the lookup algorithm terminates, there must be at least one Unusedslot (NULL key) in the table.The value ma_fill is the number of non-NULL keys (sum of Active and Dummy);ma_used is the number of non-NULL, non-dummy keys (== the number of non-NULLvalues == the number of Active items).To avoid slowing down lookups on a near-full table, we resize the table whenit's two-thirds full.*/typedef struct _dictobject PyDictObject;struct _dictobject { PyObject_HEAD Py_ssize_t ma_fill; /* # Active + # Dummy */ Py_ssize_t ma_used; /* # Active */  /* The table contains ma_mask + 1 slots, and that's a power of 2. * We store the mask instead of the size because the mask is more * frequently needed. */ Py_ssize_t ma_mask;  /* ma_table points to ma_smalltable for small tables, else to * additional malloc'ed memory. ma_table is never NULL! This rule * saves repeated runtime null-tests in the workhorse getitem and * setitem calls. */ PyDictEntry *ma_table; PyDictEntry *(*ma_lookup)(PyDictObject *mp, PyObject *key, long hash); PyDictEntry ma_smalltable[PyDict_MINSIZE];};

#ifdef Py_TRACE_REFS/* Define pointers to support a doubly-linked list of all live heap objects. */#define _PyObject_HEAD_EXTRA  / struct _object *_ob_next;  / struct _object *_ob_prev; #define _PyObject_EXTRA_INIT 0, 0, #else#define _PyObject_HEAD_EXTRA#define _PyObject_EXTRA_INIT#endif /* PyObject_HEAD defines the initial segment of every PyObject. */#define PyObject_HEAD   / _PyObject_HEAD_EXTRA  / Py_ssize_t ob_refcnt;  / struct _typeobject *ob_type;

/* PyObject_VAR_HEAD defines the initial segment of all variable-size * container objects. These end with a declaration of an array with 1 * element, but enough space is malloc'ed so that the array actually * has room for ob_size elements. Note that ob_size is an element count, * not necessarily a byte count. */#define PyObject_VAR_HEAD  / PyObject_HEAD   / Py_ssize_t ob_size; /* Number of items in variable part */

#!/usr/bin/env pythonclass Foobar(object): def __init__(self, x): self.x = x@profiledef main(): f = [Foobar(42) for i in range(1000000)]if __name__ == "__main__": main()

#!/usr/bin/env pythonclass Foobar(object): __slots__ = 'x' def __init__(self, x): self.x = x@profiledef main(): f = [Foobar(42) for i in range(1000000)]if __name__ == "__main__": main()