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Reorganize README + make examples py2/py3 compatible
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piskvorky committed Aug 4, 2018
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=============================================
smart_open -- utils for streaming large files
=============================================

|License|_ |Travis|_
======================================================
smart_open — utils for streaming large files in Python
======================================================

|License|_ |Travis|_

.. |License| image:: https://img.shields.io/pypi/l/smart_open.svg
.. |Travis| image:: https://travis-ci.org/RaRe-Technologies/smart_open.svg?branch=master
Expand All @@ -13,150 +12,145 @@ smart_open -- utils for streaming large files
What?
=====

``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 is well tested (using `moto <https://github.com/spulec/moto>`_), well documented and sports a simple, Pythonic API:
``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:

.. code-block:: python
>>> # stream lines from an S3 object
>>> for line in smart_open.smart_open('s3://mybucket/mykey.txt'):
... print line
>>> from smart_open import smart_open
>>> # using a completely custom s3 server, like s3proxy:
>>> for line in smart_open.smart_open('s3u://user:secret@host:port@mybucket/mykey.txt'):
... print line
>>> # stream lines from an S3 object
>>> for line in smart_open('s3://mybucket/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.smart_open(key) as fin:
... for line in fin:
... print line
>>> # 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.smart_open('s3://mybucket/mykey.txt') as fin:
>>> 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
... print(line.decode('utf8'))
... fin.seek(0) # seek to the beginning
... print fin.read(1000) # read 1000 bytes
... b1000 = fin.read(1000) # read 1000 bytes
>>> # stream from HDFS
>>> for line in smart_open.smart_open('hdfs://user/hadoop/my_file.txt'):
... print line
>>> for line in smart_open('hdfs://user/hadoop/my_file.txt', encoding='utf8'):
... print(line)
>>> # stream from HTTP
>>> for line in smart_open.smart_open('http://example.com/index.html'):
... print line
>>> for line in smart_open('http://example.com/index.html'):
... print(line)
>>> # stream from WebHDFS
>>> for line in smart_open.smart_open('webhdfs://host:port/user/hadoop/my_file.txt'):
... print line
>>> for line in smart_open('webhdfs://host:port/user/hadoop/my_file.txt'):
... print(line)
>>> # stream content *into* S3 (write mode):
>>> with smart_open.smart_open('s3://mybucket/mykey.txt', 'wb') as fout:
... for line in ['first line', 'second line', 'third line']:
... fout.write(line + '\n')
>>> 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.smart_open('hdfs://host:port/user/hadoop/my_file.txt', 'wb') as fout:
... for line in ['first line', 'second line', 'third line']:
... fout.write(line + '\n')
>>> 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.smart_open('webhdfs://host:port/user/hadoop/my_file.txt', 'wb') as fout:
... for line in ['first line', 'second line', 'third line']:
... fout.write(line + '\n')
>>> 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 from/to local compressed files:
>>> for line in smart_open.smart_open('./foo.txt.gz'):
... print line
>>> # stream using a completely custom s3 server, like s3proxy:
>>> for line in smart_open('s3u://user:secret@host:port@mybucket/mykey.txt', 'rb'):
... print(line.decode('utf8'))
>>> with smart_open.smart_open('/home/radim/foo.txt.bz2', 'wb') as fout:
... fout.write("some content\n")
>>> # 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'))
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):
.. code-block:: python
Why?
----

>>> # 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)
Working with large S3 files using Amazon's default Python library, `boto <http://docs.pythonboto.org/en/latest/>`_ and `boto3 <https://boto3.readthedocs.io/en/latest/>`_, 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.

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

.. code-block:: python
Installation
------------
::

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

Or, if you prefer to install from the `source tar.gz <http://pypi.python.org/pypi/smart_open>`_::

python setup.py test # run unit tests
python setup.py install

To run the unit tests (optional), you'll also need to install `mock <https://pypi.python.org/pypi/mock>`_ , `moto <https://github.com/spulec/moto>`_ and `responses <https://github.com/getsentry/responses>`_ (``pip install mock moto responses``). The tests are also run automatically with `Travis CI <https://travis-ci.org/RaRe-Technologies/smart_open>`_ 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:

.. code-block:: python
>>> smart_open.smart_open('s3://', host='s3.amazonaws.com')
>>> smart_open.smart_open('s3://', profile_name='my-profile')
>>> smart_open('s3://', host='s3.amazonaws.com')
>>> smart_open('s3://', profile_name='my-profile')
The **s3_session** argument allows you to provide a custom `boto3.Session` instance for connecting to S3:

.. code-block:: python
>>> smart_open.smart_open('s3://', s3_session=boto3.Session())
>>> smart_open('s3://', s3_session=boto3.Session())
The **s3_upload** argument accepts a dict of any parameters accepted by `initiate_multipart_upload <https://boto3.readthedocs.io/en/latest/reference/services/s3.html#S3.ObjectSummary.initiate_multipart_upload/>`_:

.. code-block:: python
>>> smart_open.smart_open('s3://', s3_upload={ 'ServerSideEncryption': 'AES256' })
The S3 reader supports gzipped content, as long as the key is obviously a gzipped file (e.g. ends with ".gz").

Why?
----

Working with large S3 files using Amazon's default Python library, `boto <http://docs.pythonboto.org/en/latest/>`_, 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, and a lot of boilerplate.

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

Installation
------------
::

pip install smart_open
>>> smart_open('s3://', s3_upload={ 'ServerSideEncryption': 'AES256' })
Or, if you prefer to install from the `source tar.gz <http://pypi.python.org/pypi/smart_open>`_::
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):

python setup.py test # run unit tests
python setup.py install
.. code-block:: python
To run the unit tests (optional), you'll also need to install `mock <https://pypi.python.org/pypi/mock>`_ , `moto <https://github.com/spulec/moto>`_ and `responses <https://github.com/getsentry/responses>` (``pip install mock moto responses``). The tests are also run automatically with `Travis CI <https://travis-ci.org/RaRe-Technologies/smart_open>`_ on every commit push & pull request.
>>> 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))
Todo
----
For more info (S3 credentials in URI, minimum S3 part size...) and full method signatures, check out the API docs:

``smart_open`` is an ongoing effort. Suggestions, pull request and improvements welcome!
.. code-block:: python
On the roadmap:
>>> import smart_open
>>> help(smart_open.smart_open_lib)
* better documentation for the default ``file://`` scheme
Comments, bug reports
---------------------

``smart_open`` lives on `github <https://github.com/RaRe-Technologies/smart_open>`_. You can file
issues or pull requests there.
``smart_open`` lives on `Github <https://github.com/RaRe-Technologies/smart_open>`_. 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 <https://github.com/piskvorky/smart_open/blob/master/LICENSE>`_.
Copyright (c) 2015-now `Radim Řehůřek <http://radimrehurek.com>`_.
Copyright (c) 2015-now `Radim Řehůřek <https://radimrehurek.com>`_.

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