On Sat, May 21, 2016 at 11:05 AM, <jf...@ms4.hinet.net> wrote: > Is there any tools which can do the memory dump of an object so I can view > their content or implementation? For example, > >>>> s1 = '\x80abc' >>>> b1 = b'\x80abc' > > What are exactly stored in memory for each of them? Is their content really > the same? This kind of tool should be helpful "for me" to learn the inner > detail of Python. >
MASSIVE CAVEAT: This is *not* anything that the Python language specifies. You can mess around with this in one interpreter (say, CPython 3.5) and get one result, but in a different interpreter (Jython, IronPython, MicroPython, Brython), or a different version of the same interpreter (CPython 3.2), or even the exact same interpreter on different platforms (32-bit vs 64-bit, Linux vs Windows vs Mac OS vs other, or different CPUs), you may get completely different results. And some language implementations (eg PyPy) don't necessarily even keep the object in memory at all times. But if you're curious about how things are stored, there are ways you can mess around and find stuff out. The easiest way to explore CPython's internals would probably be ctypes. In CPython, an object's identity is based on its address in memory, so you can cast that to a pointer. >>> import ctypes >>> s1 = "\x80abc" >>> ctypes.cast(id(s1), ctypes.c_voidp) c_void_p(140180250548144) >>> import sys >>> sys.getsizeof(s1) # See how much space it takes up in RAM 77 You can mess around with pointers to your heart's content: >>> ptr = ctypes.cast(id(s1), ctypes.POINTER(ctypes.c_uint8)) >>> bytes([ptr[i] for i in range(77)]) b'\x01\x00\x00\x00\x00\x00\x00\x00\x00\x04\x88\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x15!\xbc\x99y\xc4A]\xa43XB~\x7f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x80abc\x00' Hey look, there it is! For more info on how CPython 3.3+ stores Unicode text, check out this document: https://www.python.org/dev/peps/pep-0393/ It's pretty smart :) ChrisA -- https://mail.python.org/mailman/listinfo/python-list
