Metadata-Version: 1.1
Name: safer
Version: 4.0.0
Summary: A safer file opener
Home-page: https://github.com/rec/safer
Author: Tom Ritchford
Author-email: tom@swirly.com
License: MIT
Description: ✏️safer: a safer file opener ✏️
        -------------------------------
        
        No more partial writes or corruption! For file streams, sockets or
        any callable.
        
        Install ``safer`` from the command line with pip
        (https://pypi.org/project/pip): ``pip install safer``.
        
        Tested on Python 3.4 and 3.8
        For Python 2.7, use https://github.com/rec/safer/tree/v2.0.5
        
        See the Medium article `here. <https://medium.com/@TomSwirly/%EF%B8%8F-safer-a-safer-file-writer-%EF%B8%8F-5fe267dbe3f5>`_
        
        ``safer`` is aimed at preventing a programmer error from causing corrupt files,
        streams, socket connections or similar.  It does not prevent concurrent
        modification of files from other threads or processes: if you need atomic file
        writing, see https://pypi.org/project/atomicwrites/
        
        * ``safer.writer()`` wraps an existing writer or socket and writes a whole
          response or nothing, by caching written data in memory
        
        * ``safer.open()`` is a drop-in replacement for built-in ``open`` that
          writes a whole file or nothing by caching written data on disk.
          Unfortunately, disk caching does not work on Windows.
        
        * ``safer.closer()`` returns a stream like from ``safer.write()`` that also
          closes the underlying stream or callable when it closes.
        
        * ``safer.printer()`` is ``safer.open()`` except that it yields a
          a function that prints to the stream.  Like ``safer.open()``, it
          unfortunately does not work on Windows.
        
        By default, ``safer`` buffers the written data in memory in a ``io.StringIO``
        or ``io.BytesIO``.
        
        For very large files, ``safer.open()`` has a ``temp_file`` argument which
        writes the data to a temporary file on disk, which is moved over using
        ``os.rename`` if the operation completes successfully.
        
        ------------------
        
        ``safer.writer()``
        ==================
        
        ``safer.writer()`` wraps an existing stream - a writer, socket, or callback
        in a temporary stream which is only copied to the target stream at closer() and
        only if no exception was raised
        
        EXAMPLE
        
        .. code-block:: python
        
            sock = socket.socket(*args)
        
            # dangerous
            try:
                write_header(sock)
                write_body(sock)   # Exception is thrown here
                write_footer(sock)
             except:
                write_error(sock)  # Oops, the header was already written
        
            # safer
            try:
                with safer.writer(sock) as s:
                    write_header(s)
                    write_body(s)  # Exception is thrown here
                    write_footer(s)
             except:
                write_error(sock)  # Nothing has been written
        
        ``safer.open()``
        =================
        
        Writes a whole file or nothing. It's a drop-in replacement for built-in
        ``open()`` except that ``safer.open()`` leaves the original file unchanged on
        failure.
        
        EXAMPLE
        
        .. code-block:: python
        
            # dangerous
            with open(filename, 'w') as fp:
                json.dump(data, fp)
                # If an exception is raised, the file is empty or partly written
        
            # safer
            with safer.open(filename, 'w') as fp:
                json.dump(data, fp)
                # If an exception is raised, the file is unchanged.
        
        
        ``safer.open(filename)`` returns a file stream ``fp`` like ``open(filename)``
        would, except that ``fp`` writes to memory stream or a a temporary file in the
        same directory.
        
        If ``fp`` is used as a context manager and an exception is raised, then
        ``fp.safer_failed`` is automatically set to ``True``. And when ``fp.close()``
        is called, the cached data is stored in ``filename`` *unless*
        ``fp.safer_failed`` is true.
        
        ------------------------------------
        
        ``safer.printer()``
        ===================
        
        ``safer.printer()`` is similar to ``safer.open()`` except it yields a function
        that prints to the open file - it's very convenient for printing text.
        
        Like ``safer.open()``, if an exception is raised within its context manager,
        the original file is left unchanged.
        
        EXAMPLE
        
        .. code-block:: python
        
            # dangerous
            with open(file, 'w') as fp:
                for item in items:
                    print(item, file=fp)
                # Prints lines until the first exception
        
            # safer
            with safer.printer(file) as print:
                for item in items:
                    print(item)
                # Either the whole file is written, or nothing
        
        FUNCTIONS
        ---------
        
        ``safer.writer(stream, is_binary=None, close_on_exit=False, temp_file=False, chunk_size=1048576, delete_failures=True)``
        ========================================================================================================================
        
            Write safely to file streams, sockets and callables.
        
            ``safer.writer`` yields an in-memory stream that you can write
            to, but which is only written to the original stream if the
            context finished without raising an exception.
        
            Because the actual writing happens when the context exits, it's possible
            to block indefinitely if the underlying socket, stream or callable does.
        
            ARGUMENTS
              stream:
                A file stream, a socket, or a callable that will receive data
        
              is_binary:
                Is ``stream`` a binary stream?
        
                If ``is_binary`` is ``None``, deduce whether it's a binary file from
                the stream, or assume it's text otherwise.
        
              close_on_exit: If True, the underlying stream is closed when the writer
                closes
        
              temp_file:
                If not false, use a disk file and os.rename() at the end, otherwise
                cache the writes in memory.  If it's a string, use this as the
                name of the temporary file, otherwise select one in the same
                directory as the target file, or in the system tempfile for streams
                that aren't files.
        
              chunk_size:
                Transfer data from the temporary file to the underlying stream in
                chunks of this byte size
        
              delete_failures:
                If set to false, any temporary files created are not deleted
                if there is an exception
            
        
        ``safer.open(name, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None, follow_symlinks=True, make_parents=False, delete_failures=True, temp_file=False)``
        ==================================================================================================================================================================================================
        
            A drop-in replacement for ``open()`` which returns a stream which only
            overwrites the original file when close() is called, and only if there was
            no failure.
        
            If a stream ``fp`` return from ``safer.open()`` is used as a context
            manager and an exception is raised, the property ``fp.safer_failed`` is
            set to ``True``.
        
            In the method ``fp.close()``, if ``fp.safer_failed`` is *not* set, then the
            cached results replace the original file, successfully completing the
            write.
        
            If ``fp.safer_failed`` is true, then if ``delete_failures`` is true, the
            temporary file is deleted.
        
            If the ``mode`` argument contains either ``'a'`` (append), or ``'+'``
            (update), then the original file will be copied to the temporary file
            before writing starts.
        
            Note that if the ``temp_file`` argument is set, ``safer`` uses an extra
            temporary file which is renamed over the file only after the stream closes
            without failing. This uses as much disk space as the old and new files put
            together.
        
            ARGUMENTS
        
            The arguments mean the same as for built-in ``open()``, except these:
        
              follow_symlinks:
                If true, overwrite the file pointed to and not the symlink
        
              make_parents:
                If true, create the parent directory of the file if it doesn't exist
        
              delete_failures:
                If set to false, any temporary files created are not deleted
                if there is an exception
        
              temp_file:
                If true, use a disk file and os.rename() at the end, otherwise
                cache the writes in memory.  If it's a string, use this as the
                name of the temporary file, otherwise select one in the same
                directory as the target file, or in the system tempfile for streams
                that aren't files.
            
        
        ``safer.closer(stream, is_binary=None, close_on_exit=False)``
        =============================================================
        
            Like ``safer.writer()`` but with ``close_on_exit=True`` by default
        
            ARGUMENTS
              stream:
                A file stream, a socket, or a callable that will receive data
        
              is_binary:
                Is ``stream`` a binary stream?
        
                If ``is_binary`` is ``None``, deduce whether it's a binary file from
                the stream, or assume it's text otherwise.
        
              close_on_exit: If True, the underlying stream is closed when the writer
                closes
            
        
        ``safer.printer(name, mode='w', *args, **kwargs)``
        ==================================================
        
            A context manager that yields a function that prints to the opened file,
            only writing to the original file at the exit of the context,
            and only if there was no exception thrown
        
            ARGUMENTS
              Same as for ``safer.open()``
        
Keywords: testing,modules
Platform: UNKNOWN
Classifier: Development Status :: 5 - Production/Stable
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 3.4
Classifier: Programming Language :: Python :: 3.5
Classifier: Programming Language :: Python :: 3.6
Classifier: Programming Language :: Python :: 3.7
Classifier: Programming Language :: Python :: 3.8
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: MIT License
Classifier: Topic :: Software Development :: Libraries
Classifier: Topic :: Utilities
