dask.bag.to_textfiles

dask.bag.to_textfiles¶

dask.bag.to_textfiles(b, path, name_function=None, compression='infer', encoding='utf-8', compute=True, storage_options=None, last_endline=False, **kwargs)[source]¶

Write dask Bag to disk, one filename per partition, one line per element.

Paths: This will create one file for each partition in your bag. You can specify the filenames in a variety of ways.

Use a globstring

>>> b.to_textfiles('/path/to/data/*.json.gz')  

The * will be replaced by the increasing sequence 1, 2, …

/path/to/data/0.json.gz
/path/to/data/1.json.gz

Use a globstring and a name_function= keyword argument. The name_function function should expect an integer and produce a string. Strings produced by name_function must preserve the order of their respective partition indices.

>>> from datetime import date, timedelta
>>> def name(i):
...     return str(date(2015, 1, 1) + i * timedelta(days=1))

>>> name(0)
'2015-01-01'
>>> name(15)
'2015-01-16'

>>> b.to_textfiles('/path/to/data/*.json.gz', name_function=name)  

/path/to/data/2015-01-01.json.gz
/path/to/data/2015-01-02.json.gz
...

You can also provide an explicit list of paths.

>>> paths = ['/path/to/data/alice.json.gz', '/path/to/data/bob.json.gz', ...]  
>>> b.to_textfiles(paths) 

Compression: Filenames with extensions corresponding to known compression algorithms (gz, bz2) will be compressed accordingly.

Bag Contents: The bag calling to_textfiles must be a bag of text strings. For example, a bag of dictionaries could be written to JSON text files by mapping json.dumps on to the bag first, and then calling to_textfiles :

>>> b_dict.map(json.dumps).to_textfiles("/path/to/data/*.json")  

Last endline: By default the last line does not end with a newline character. Pass last_endline=True to invert the default.

dask.bag.map_partitions

dask.bag.zip