pyarrow.MemoryMappedFile

class pyarrow.MemoryMappedFile

Bases: 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 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.

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 data to the file.

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 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

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 data to the file.

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

nbytes: number of bytes written

writelines(self, lines)