Looking for info on Python's memory allocation

[jepler at unpythonic.net]

While there may be a discussion somewhere in the archives,
the comments in listobject.c are enlightening too.

/* Ensure ob_item has room for at least newsize elements, and set
 * ob_size to newsize.  If newsize > ob_size on entry, the content
 * of the new slots at exit is undefined heap trash; it's the caller's
 * responsiblity to overwrite them with sane values.
 * The number of allocated elements may grow, shrink, or stay the same.
 * Failure is impossible if newsize <= self.allocated on entry, although
 * that partly relies on an assumption that the system realloc() never
 * fails when passed a number of bytes <= the number of bytes last
 * allocated (the C standard doesn't guarantee this, but it's hard to
 * imagine a realloc implementation where it wouldn't be true).
 * Note that self->ob_item may change, and even if newsize is less
 * than ob_size on entry.
 */
[...]
/* This over-allocates proportional to the list size, making room
 * for additional growth.  The over-allocation is mild, but is
 * enough to give linear-time amortized behavior over a long
 * sequence of appends() in the presence of a poorly-performing
 * system realloc().
 * The growth pattern is:  0, 4, 8, 16, 25, 35, 46, 58, 72, 88, ...
 */
"linear-time amortized behavior" (i.e., that list.append() is O(1) on average)
is the important characteristic you're probably looking for.

CVS source for listobject.c can be seen here:
	http://cvs.sourceforge.net/viewcvs.py/python/python/dist/src/Objects/listobject.c?rev=2.227&view=markup

Jeff
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