pyarrow.MemoryMappedFile#

class pyarrow.MemoryMappedFile#

Bases: pyarrow.lib.NativeFile

A stream that represents a memory-mapped file.

Supports ‘r’, ‘r+’, ‘w’ modes.

__init__(*args, **kwargs)#

Methods

__init__(*args, **kwargs)

close(self)

create(path, size)

Create a MemoryMappedFile

download(self, stream_or_path[, buffer_size])

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

fileno(self)

flush(self)

Flush the stream, if applicable.

isatty(self)

metadata(self)

Return file metadata

read(self[, nbytes])

Read indicated number of bytes from file, or read all remaining bytes if no argument passed

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.

resize(self, new_size)

Resize the map and underlying file.

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

Change current file stream position

seekable(self)

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 byte from any object implementing buffer protocol (bytes, bytearray, ndarray, pyarrow.Buffer)

writelines(self, lines)

Attributes

closed

mode

The file mode.
close(self)#
closed#
static create(path, size)#

Create a MemoryMappedFile

Parameters
pathstr

Where to create the file.

sizeint

Size of the memory mapped file.

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)#
flush(self)#

Flush the stream, if applicable.

An error is raised if stream is not writable.

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 indicated number of bytes from file, or read all remaining bytes if no argument passed

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

Read and return up to n bytes.

Alias for read, needed to match the BufferedIOBase interface.

Parameters
nbytesint

The maximum number of bytes to read.

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

resize(self, new_size)#

Resize the map and underlying file.

Parameters
new_sizenew size in bytes
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)#
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 byte from any object implementing buffer protocol (bytes, bytearray, ndarray, pyarrow.Buffer)

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

nbytes: number of bytes written

writelines(self, lines)#

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