Source code for dask.bag.text

import io
import os
from functools import partial

from tlz import concat

from ..bytes import open_files, read_bytes
from ..delayed import delayed
from ..utils import parse_bytes, system_encoding
from .core import from_delayed

delayed = delayed(pure=True)


[docs]def read_text( urlpath, blocksize=None, compression="infer", encoding=system_encoding, errors="strict", linedelimiter=os.linesep, collection=True, storage_options=None, files_per_partition=None, include_path=False, ): """Read lines from text files Parameters ---------- urlpath : string or list Absolute or relative filepath(s). Prefix with a protocol like ``s3://`` to read from alternative filesystems. To read from multiple files you can pass a globstring or a list of paths, with the caveat that they must all have the same protocol. blocksize: None, int, or str Size (in bytes) to cut up larger files. Streams by default. Can be ``None`` for streaming, an integer number of bytes, or a string like "128MiB" compression: string Compression format like 'gzip' or 'xz'. Defaults to 'infer' encoding: string errors: string linedelimiter: string collection: bool, optional Return dask.bag if True, or list of delayed values if false storage_options: dict Extra options that make sense to a particular storage connection, e.g. host, port, username, password, etc. files_per_partition: None or int If set, group input files into partitions of the requested size, instead of one partition per file. Mutually exclusive with blocksize. include_path: bool Whether or not to include the path in the bag. If true, elements are tuples of (line, path). Default is False. Examples -------- >>> b = read_text('myfiles.1.txt') # doctest: +SKIP >>> b = read_text('myfiles.*.txt') # doctest: +SKIP >>> b = read_text('myfiles.*.txt.gz') # doctest: +SKIP >>> b = read_text('s3://bucket/myfiles.*.txt') # doctest: +SKIP >>> b = read_text('s3://key:secret@bucket/myfiles.*.txt') # doctest: +SKIP >>> b = read_text('hdfs://namenode.example.com/myfiles.*.txt') # doctest: +SKIP Parallelize a large file by providing the number of uncompressed bytes to load into each partition. >>> b = read_text('largefile.txt', blocksize='10MB') # doctest: +SKIP Get file paths of the bag by setting include_path=True >>> b = read_text('myfiles.*.txt', include_path=True) # doctest: +SKIP >>> b.take(1) # doctest: +SKIP (('first line of the first file', '/home/dask/myfiles.0.txt'),) Returns ------- dask.bag.Bag or list dask.bag.Bag if collection is True or list of Delayed lists otherwise. See Also -------- from_sequence: Build bag from Python sequence """ if blocksize is not None and files_per_partition is not None: raise ValueError("Only one of blocksize or files_per_partition can be set") if isinstance(blocksize, str): blocksize = parse_bytes(blocksize) files = open_files( urlpath, mode="rt", encoding=encoding, errors=errors, compression=compression, **(storage_options or {}) ) if blocksize is None: if files_per_partition is None: blocks = [ delayed(list)(delayed(partial(file_to_blocks, include_path))(fil)) for fil in files ] else: blocks = [] for start in range(0, len(files), files_per_partition): block_files = files[start : (start + files_per_partition)] block_lines = delayed(concat)( delayed(map)( partial(file_to_blocks, include_path), block_files, ) ) blocks.append(block_lines) else: o = read_bytes( urlpath, delimiter=linedelimiter.encode(), blocksize=blocksize, sample=False, compression=compression, include_path=include_path, **(storage_options or {}) ) raw_blocks = o[1] blocks = [delayed(decode)(b, encoding, errors) for b in concat(raw_blocks)] if include_path: paths = list( concat([[path] * len(raw_blocks[i]) for i, path in enumerate(o[2])]) ) blocks = [ delayed(attach_path)(entry, path) for entry, path in zip(blocks, paths) ] if not blocks: raise ValueError("No files found", urlpath) if collection: blocks = from_delayed(blocks) return blocks
def file_to_blocks(include_path, lazy_file): with lazy_file as f: for line in f: yield (line, lazy_file.path) if include_path else line def attach_path(block, path): for p in block: yield (p, path) def decode(block, encoding, errors): text = block.decode(encoding, errors) lines = io.StringIO(text) return list(lines)