pyin 0.4

pyin
====

[](https://travis-ci.org/geowurster/pyin) [](https://coveralls.io/r/geowurster/pyin?branch=master)

Perform Python operations on every line read from `stdin`. Every line is
evaluated individually and available via a variable called `line`.


Installing
----------

Via pip:

$ pip install git+https://github.com/geowurster/pyin.git

From master branch:

$ git clone https://github.com/geowurster/pyin
$ pip install -e .


Examples
--------

Change newline character in a CSV.

$ more sample-data/csv-with-header.csv | pyin "line.replace('\n', '\r\n')" > output.csv

Extract a BigQuery schema from an existing table and pretty print it:

```console
$ bq show --format=json ${DATASET}.${TABLE} | pyin -m json -m pprint "pprint.pformat(json.loads(line)['schema']['fields'])"
[{u'mode': u'NULLABLE', u'name': u'mmsi', u'type': u'STRING'},
{u'mode': u'NULLABLE', u'name': u'longitude', u'type': u'FLOAT'},
{u'mode': u'NULLABLE', u'name': u'latitude', u'type': u'FLOAT'}
...]
```

Read the first 100K lines of a CSV and write the

head -100000 ${INFILE} | pyin -r csv.DictReader -m csv "line['Msg type'] == '5'" -n -t -l '' -w newlinejson.Writer -m newlinejson -wm writerow > ~/github/VesselInfo/Data/100K-Sample-Type5.json




Gotchas
-------

It's easy to completely modify the line content:

$ pyin -i sample-data/csv-with-header.csv "'operation'"
operationoperationoperationoperationoperationoperation

Forgetting to use `-t` to only get lines that evaluate as `True`:

$ pyin -i LICENSE.txt "'are' in line"
FalseFalseFalseFalseFalseFalseTrueFalseFalseFalseFalseFalseFalseFalseFalseFalseTrueFalseFalseFalseFalseFalseFalseFalseFalseFalseFalseFalse

$ pyin -i LICENSE.txt "'are' in line" -t
modification, are permitted provided that the following conditions are met:
derived from this software without specific prior written permission.

Specifying JSON:

$ -ro fieldnames='["field1","field2"]'

Get a list of variables available by default to the `operation` argument:

$ cat LICENSE.txt | pyin line -s "print(globals().keys()); exit()"
['main', '_str2type', '_STR_TYPES', '__all__', '_os', '__builtins__', '__source__', '__file__', '_click', '_DefaultReader', '_sys', '__package__', '__email__', '__author__', '_PY3', 'pyin', '__name__', '__version__', '__license__', '__doc__', '_DefaultWriter']

The `--reader-option key=val` values are parsed to their Python type but if the user wants to
specify something like which JSON library to use for a `newlinejson.Reader()`
instance then they must do that via the `--statement` option:

$ pyin \
-i measures.json \
-o ~/dec-type5.json \
-r newlinejson.Reader \
-s "newlinejson.core.JSON = ujson" \
-w newlinejson.Writer \
-im newlinejson \
-t "'type' in line and line['type'] is 5" \
-im ujson



Developing
----------

Install:

$ pip install virtualenv
$ git clone https://github.com/geowurster/pyin
$ cd pyin
$ virtualenv venv
$ source venv/bin/activate
$ pip install -r requirements-dev.txt
$ pip install -e .

Test:

$ nosetests

Coverage:

$ nosetests --with-coverage

Lint:

$ pep8 --max-line-length=120 pyin.py