pyarrow.FixedSizeBufferWriter

class pyarrow.FixedSizeBufferWriter

Bases: NativeFile

A stream writing to a Arrow buffer.

Examples

Create a stream to write to pyarrow.Buffer:

>>> import pyarrow as pa
>>> buf = pa.allocate_buffer(5)
>>> with pa.output_stream(buf) as stream:
...     stream.write(b'abcde')
...     stream
...
5
<pyarrow.FixedSizeBufferWriter closed=False own_file=False is_seekable=False is_writable=True is_readable=False>

Inspect the buffer:

>>> buf.to_pybytes()
b'abcde'
>>> buf
<pyarrow.Buffer address=... size=5 is_cpu=True is_mutable=True>
__init__(*args, **kwargs)

Methods

__init__(*args, **kwargs)

close(self)

download(self, stream_or_path[, buffer_size])

Read this file completely to a local path or destination stream.

fileno(self)

NOT IMPLEMENTED

flush(self)

Flush the stream, if applicable.

get_stream(self, file_offset, nbytes)

Return an input stream that reads a file segment independent of the state of the file.

isatty(self)

metadata(self)

Return file metadata

read(self[, nbytes])

Read and return up to n bytes.

read1(self[, nbytes])

Read and return up to n bytes.

read_at(self, nbytes, offset)

Read indicated number of bytes at offset from the file

read_buffer(self[, nbytes])

readable(self)

readall(self)

readinto(self, b)

Read into the supplied buffer

readline(self[, size])

NOT IMPLEMENTED.

readlines(self[, hint])

NOT IMPLEMENTED.

seek(self, int64_t position, int whence=0)

Change current file stream position

seekable(self)

set_memcopy_blocksize(self, int64_t blocksize)

set_memcopy_threads(self, int num_threads)

set_memcopy_threshold(self, int64_t threshold)

size(self)

Return file size

tell(self)

Return current stream position

truncate(self)

NOT IMPLEMENTED

upload(self, stream[, buffer_size])

Write from a source stream to this file.

writable(self)

write(self, data)

Write data to the file.

writelines(self, lines)

Attributes

closed

mode

The file mode.

close(self)
closed
download(self, stream_or_path, buffer_size=None)

Read this file completely to a local path or destination stream.

This method first seeks to the beginning of the file.

Parameters:
stream_or_pathstr or file-like object

If a string, a local file path to write to; otherwise, should be a writable stream.

buffer_sizeint, optional

The buffer size to use for data transfers.

fileno(self)

NOT IMPLEMENTED

flush(self)

Flush the stream, if applicable.

An error is raised if stream is not writable.

get_stream(self, file_offset, nbytes)

Return an input stream that reads a file segment independent of the state of the file.

Allows reading portions of a random access file as an input stream without interfering with each other.

Parameters:
file_offsetint
nbytesint
Returns:
streamNativeFile
isatty(self)
metadata(self)

Return file metadata

mode

The file mode. Currently instances of NativeFile may support:

  • rb: binary read

  • wb: binary write

  • rb+: binary read and write

read(self, nbytes=None)

Read and return up to n bytes.

If nbytes is None, then the entire remaining file contents are read.

Parameters:
nbytesint, default None
Returns:
databytes
read1(self, nbytes=None)

Read and return up to n bytes.

Unlike read(), if nbytes is None then a chunk is read, not the entire file.

Parameters:
nbytesint, default None

The maximum number of bytes to read.

Returns:
databytes
read_at(self, nbytes, offset)

Read indicated number of bytes at offset from the file

Parameters:
nbytesint
offsetint
Returns:
databytes
read_buffer(self, nbytes=None)
readable(self)
readall(self)
readinto(self, b)

Read into the supplied buffer

Parameters:
bbuffer-like object

A writable buffer object (such as a bytearray).

Returns:
writtenint

number of bytes written

readline(self, size=None)

NOT IMPLEMENTED. Read and return a line of bytes from the file.

If size is specified, read at most size bytes.

Line terminator is always b”n”.

Parameters:
sizeint

maximum number of bytes read

readlines(self, hint=None)

NOT IMPLEMENTED. Read lines of the file

Parameters:
hintint

maximum number of bytes read until we stop

seek(self, int64_t position, int whence=0)

Change current file stream position

Parameters:
positionint

Byte offset, interpreted relative to value of whence argument

whenceint, default 0

Point of reference for seek offset

Returns:
int

The new absolute stream position.

Notes

Values of whence: * 0 – start of stream (the default); offset should be zero or positive * 1 – current stream position; offset may be negative * 2 – end of stream; offset is usually negative

seekable(self)
set_memcopy_blocksize(self, int64_t blocksize)
set_memcopy_threads(self, int num_threads)
set_memcopy_threshold(self, int64_t threshold)
size(self)

Return file size

tell(self)

Return current stream position

truncate(self)

NOT IMPLEMENTED

upload(self, stream, buffer_size=None)

Write from a source stream to this file.

Parameters:
streamfile-like object

Source stream to pipe to this file.

buffer_sizeint, optional

The buffer size to use for data transfers.

writable(self)
write(self, data)

Write data to the file.

Parameters:
databytes-like object or exporter of buffer protocol
Returns:
int

nbytes: number of bytes written

writelines(self, lines)