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author | Erlend Egeberg Aasland <erlend.aasland@innova.no> | 2022-04-16 13:28:38 (GMT) |
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committer | GitHub <noreply@github.com> | 2022-04-16 13:28:38 (GMT) |
commit | 95573ade42d1635dd9b69380117cbb47b6790772 (patch) | |
tree | 40bd29e509dd55dbdac9a5a71654e2b94c7680ca /Doc | |
parent | f2bc12f0d5297899b57f3fa688b24f3c1d1bee7b (diff) | |
download | cpython-95573ade42d1635dd9b69380117cbb47b6790772.zip cpython-95573ade42d1635dd9b69380117cbb47b6790772.tar.gz cpython-95573ade42d1635dd9b69380117cbb47b6790772.tar.bz2 |
gh-69093: sqlite3 blob doc amendments (GH-91561)
- document that you cannot open a blob handle in a WITHOUT ROWID table
- document the blobopen() positional arguments in the same order as they
appear
- relocate sqlite3.Blob section
Diffstat (limited to 'Doc')
-rw-r--r-- | Doc/library/sqlite3.rst | 107 |
1 files changed, 55 insertions, 52 deletions
diff --git a/Doc/library/sqlite3.rst b/Doc/library/sqlite3.rst index 4838db0..5c9e2e8 100644 --- a/Doc/library/sqlite3.rst +++ b/Doc/library/sqlite3.rst @@ -397,9 +397,12 @@ Connection Objects .. method:: blobopen(table, column, row, /, *, readonly=False, name="main") Open a :class:`Blob` handle to the :abbr:`BLOB (Binary Large OBject)` - located in row *row*, column *column*, table *table* of database *name*. + located in table name *table*, column name *column*, and row index *row* + of database *name*. When *readonly* is :const:`True` the blob is opened without write permissions. + Trying to open a blob in a ``WITHOUT ROWID`` table will raise + :exc:`OperationalError`. .. note:: @@ -1044,6 +1047,57 @@ Now we plug :class:`Row` in:: 35.14 +Blob Objects +------------ + +.. versionadded:: 3.11 + +.. class:: Blob + + A :class:`Blob` instance is a :term:`file-like object` that can read and write + data in an SQLite :abbr:`BLOB (Binary Large OBject)`. Call ``len(blob)`` to + get the size (number of bytes) of the blob. + + Use the :class:`Blob` as a :term:`context manager` to ensure that the blob + handle is closed after use. + + .. literalinclude:: ../includes/sqlite3/blob.py + + .. method:: close() + + Close the blob. + + The blob will be unusable from this point onward. An + :class:`~sqlite3.Error` (or subclass) exception will be raised if any + further operation is attempted with the blob. + + .. method:: read(length=-1, /) + + Read *length* bytes of data from the blob at the current offset position. + If the end of the blob is reached, the data up to + :abbr:`EOF (End of File)` will be returned. When *length* is not + specified, or is negative, :meth:`~Blob.read` will read until the end of + the blob. + + .. method:: write(data, /) + + Write *data* to the blob at the current offset. This function cannot + change the blob length. Writing beyond the end of the blob will raise + :exc:`ValueError`. + + .. method:: tell() + + Return the current access position of the blob. + + .. method:: seek(offset, origin=os.SEEK_SET, /) + + Set the current access position of the blob to *offset*. The *origin* + argument defaults to :data:`os.SEEK_SET` (absolute blob positioning). + Other values for *origin* are :data:`os.SEEK_CUR` (seek relative to the + current position) and :data:`os.SEEK_END` (seek relative to the blob’s + end). + + .. _sqlite3-exceptions: Exceptions @@ -1104,57 +1158,6 @@ Exceptions .. _sqlite3-blob-objects: -Blob Objects ------------- - -.. versionadded:: 3.11 - -.. class:: Blob - - A :class:`Blob` instance is a :term:`file-like object` that can read and write - data in an SQLite :abbr:`BLOB (Binary Large OBject)`. Call ``len(blob)`` to - get the size (number of bytes) of the blob. - - Use the :class:`Blob` as a :term:`context manager` to ensure that the blob - handle is closed after use. - - .. literalinclude:: ../includes/sqlite3/blob.py - - .. method:: close() - - Close the blob. - - The blob will be unusable from this point onward. An - :class:`~sqlite3.Error` (or subclass) exception will be raised if any - further operation is attempted with the blob. - - .. method:: read(length=-1, /) - - Read *length* bytes of data from the blob at the current offset position. - If the end of the blob is reached, the data up to - :abbr:`EOF (End of File)` will be returned. When *length* is not - specified, or is negative, :meth:`~Blob.read` will read until the end of - the blob. - - .. method:: write(data, /) - - Write *data* to the blob at the current offset. This function cannot - change the blob length. Writing beyond the end of the blob will raise - :exc:`ValueError`. - - .. method:: tell() - - Return the current access position of the blob. - - .. method:: seek(offset, origin=os.SEEK_SET, /) - - Set the current access position of the blob to *offset*. The *origin* - argument defaults to :data:`os.SEEK_SET` (absolute blob positioning). - Other values for *origin* are :data:`os.SEEK_CUR` (seek relative to the - current position) and :data:`os.SEEK_END` (seek relative to the blob’s - end). - - .. _sqlite3-types: SQLite and Python types |