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| -rw-r--r-- | Doc/whatsnew/2.7.rst | 54 |
1 files changed, 53 insertions, 1 deletions
diff --git a/Doc/whatsnew/2.7.rst b/Doc/whatsnew/2.7.rst index d687cf0def..84050d4d1b 100644 --- a/Doc/whatsnew/2.7.rst +++ b/Doc/whatsnew/2.7.rst @@ -8,7 +8,7 @@ .. Fix accents on Kristjan Valur Jonsson, Fuerstenau -.. Big jobs: ElementTree 1.3, pep 391, sysconfig, memoryview +.. Big jobs: ElementTree 1.3, pep 391, sysconfig .. unittest test discovery .. hyperlink all the methods & functions. @@ -435,6 +435,58 @@ converter will change them to the standard :meth:`keys`, Backported to 2.7 by Alexandre Vassalotti; :issue:`1967`. +PEP 3137: The memoryview Object +==================================================== + +The :class:`memoryview` object provides a view of another object's +memory content that matches the :class:`bytes` type's interface. + + >>> import string + >>> m = memoryview(string.letters) + >>> m + <memory at 0x37f850> + >>> len(m) # Returns length of underlying object + 52 + >>> m[0], m[25], m[26] # Indexing returns one byte + ('a', 'z', 'A') + >>> m2 = m[0:26] # Slicing returns another memoryview + >>> m2 + <memory at 0x37f080> + +The content of the view can be converted to a string of bytes or to +a list of integers: + + >>> m2.tobytes() + 'abcdefghijklmnopqrstuvwxyz' + >>> m2.tolist() + [97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122] + >>> + +:class:`memoryview` objects allow modifying the underlying object if +it's a mutable object. + + >>> m2[0] = 75 + Traceback (most recent call last): + File "<stdin>", line 1, in <module> + TypeError: cannot modify read-only memory + >>> b = bytearray(string.letters) # Creating a mutable object + >>> b + bytearray(b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ') + >>> mb = memoryview(b) + >>> mb[0] = '*' # Assign to view, changing the bytearray. + >>> b[0:5] # The bytearray has been changed. + bytearray(b'*bcde') + >>> + +.. seealso:: + + :pep:`3137` - Immutable Bytes and Mutable Buffer + PEP written by Guido van Rossum. + Implemented by Travis Oliphant. + Backported to 2.7 by Antoine Pitrou; :issue:`2396`. + + + Other Language Changes ====================== |