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Last Commit
Aug. 16, 2018
Jan. 2, 2015

smart_open — utils for streaming large files in Python

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smart_open is a Python 2 & Python 3 library for efficient streaming of very large files from/to S3, HDFS, WebHDFS, HTTP, or local (compressed) files. It's a drop-in replacement for Python's built-in open(): it can do anything open can (100% compatible, falls back to native open wherever possible), plus lots of nifty extra stuff on top.

smart_open is well-tested, well-documented and sports a simple, Pythonic API:

>>> from smart_open import smart_open

>>> # stream lines from an S3 object
>>> for line in smart_open('s3://mybucket/mykey.txt', 'rb'):
...    print(line.decode('utf8'))

>>> # stream from/to compressed files, with transparent (de)compression:
>>> for line in smart_open('./foo.txt.gz', encoding='utf8'):
...    print(line)

>>> # can use context managers too:
>>> with smart_open('/home/radim/foo.txt.bz2', 'wb') as fout:
...    fout.write(u"some content\n".encode('utf8'))

>>> with smart_open('s3://mybucket/mykey.txt', 'rb') as fin:
...     for line in fin:
...         print(line.decode('utf8'))
...  # seek to the beginning
...     b1000 =  # read 1000 bytes

>>> # stream from HDFS
>>> for line in smart_open('hdfs://user/hadoop/my_file.txt', encoding='utf8'):
...     print(line)

>>> # stream from HTTP
>>> for line in smart_open(''):
...     print(line)

>>> # stream from WebHDFS
>>> for line in smart_open('webhdfs://host:port/user/hadoop/my_file.txt'):
...     print(line)

>>> # stream content *into* S3 (write mode):
>>> with smart_open('s3://mybucket/mykey.txt', 'wb') as fout:
...     for line in [b'first line\n', b'second line\n', b'third line\n']:
...          fout.write(line)

>>> # stream content *into* HDFS (write mode):
>>> with smart_open('hdfs://host:port/user/hadoop/my_file.txt', 'wb') as fout:
...     for line in [b'first line\n', b'second line\n', b'third line\n']:
...          fout.write(line)

>>> # stream content *into* WebHDFS (write mode):
>>> with smart_open('webhdfs://host:port/user/hadoop/my_file.txt', 'wb') as fout:
...     for line in [b'first line\n', b'second line\n', b'third line\n']:
...          fout.write(line)

>>> # stream using a completely custom s3 server, like s3proxy:
>>> for line in smart_open('s3u://user:[email protected]:[email protected]/mykey.txt', 'rb'):
...    print(line.decode('utf8'))

>>> # you can also use a boto.s3.key.Key instance directly:
>>> key = boto.connect_s3().get_bucket("my_bucket").get_key("my_key")
>>> with smart_open(key, 'rb') as fin:
...     for line in fin:
...         print(line.decode('utf8'))


Working with large S3 files using Amazon's default Python library, boto and boto3, is a pain. Its key.set_contents_from_string() and key.get_contents_as_string() methods only work for small files (loaded in RAM, no streaming). There are nasty hidden gotchas when using boto's multipart upload functionality that is needed for large files, and a lot of boilerplate.

smart_open shields you from that. It builds on boto3 but offers a cleaner, Pythonic API. The result is less code for you to write and fewer bugs to make.


pip install smart_open

Or, if you prefer to install from the source tar.gz:

python test  # run unit tests
python install

To run the unit tests (optional), you'll also need to install mock , moto and responses (pip install mock moto responses). The tests are also run automatically with Travis CI on every commit push & pull request.

S3-Specific Options

The S3 reader supports gzipped content transparently, as long as the key is obviously a gzipped file (e.g. ends with ".gz").

There are a few optional keyword arguments that are useful only for S3 access.

The host and profile arguments are both passed to boto.s3_connect() as keyword arguments:

>>> smart_open('s3://', host='')
>>> smart_open('s3://', profile_name='my-profile')

The s3_session argument allows you to provide a custom boto3.Session instance for connecting to S3:

>>> smart_open('s3://', s3_session=boto3.Session())

The s3_upload argument accepts a dict of any parameters accepted by initiate_multipart_upload:

>>> smart_open('s3://', s3_upload={ 'ServerSideEncryption': 'AES256' })

Since going over all (or select) keys in an S3 bucket is a very common operation, there's also an extra method smart_open.s3_iter_bucket() that does this efficiently, processing the bucket keys in parallel (using multiprocessing):

>>> from smart_open import smart_open, s3_iter_bucket
>>> # get all JSON files under "mybucket/foo/"
>>> bucket = boto.connect_s3().get_bucket('mybucket')
>>> for key, content in s3_iter_bucket(bucket, prefix='foo/', accept_key=lambda key: key.endswith('.json')):
...     print(key, len(content))

For more info (S3 credentials in URI, minimum S3 part size...) and full method signatures, check out the API docs:

>>> import smart_open
>>> help(smart_open.smart_open_lib)

Comments, bug reports

smart_open lives on Github. You can file issues or pull requests there. Suggestions, pull requests and improvements welcome!

smart_open is open source software released under the MIT license. Copyright (c) 2015-now Radim Řehůřek.

Latest Releases
 Jun. 29 2018
 Apr. 1 2018
 Mar. 18 2018
 Dec. 27 2017
 Dec. 6 2017