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OWith: one liner with

Do you want to reduce the number of characters in your python codes?

Regarding with statement, OWith helps you.

Introduction

Python with statement is useful. A little bit long python script like

import json
f = open("sample.json")
try:
    dic = json.load(f)
finally:
    f.close()

becomes the following short script like

import json
with open("sample.json") as f:
    dic = json.load(f)

with with. Also, using with, __enter__ and __exit__ methods of a context manager are called automatically. For example, you can use your custom context manager

class CustomCM:
    def __enter__(self):
        print("Start")
    def __exit__(self):
        print("End")

with with like the followings.

>>> with CustomCM():
...     print("Excecution")
...
start
Execution
end

As above, needless to say, with is quite helpful for you to write python codes.

However, OWith provides you an alternative tool which enables you to write fewer characters when you use with to execute one-line suite. OWith also enables you to use close or __exit__ required objects like open("sample.json") in list comprehensions and so on with the confidence that it is safe.

Installation

Requirements

  • Python >= 3.7

User Installation

pip install git+https://github.com/hmasdev/owith.git@master

How to Use

OWith provides three functions:

  1. owith: a functional like functools.partial which help you to use with;
  2. owith_all: a decorator which help you to create a function in which the arguments will be used in with statement;
  3. dcwith: a function to create a decorator which enable you to use with outside of a decorated function.

1st function: owith(func: typing.Callable, *args, **kwargs) -> typing.Callable

When writing

with some_context_manager as scm:
    ret = some_function(scm)

, you can alternatively write

ret = owith(some_function, scm)

with owith. When some_function is able to received scm as a keyword argument kwarg in the above example, you can also write

ret = owith(some_function, kwarg=scm)

with owith. Of course, owith can receive context managers at once like

ret = owith(some_function, cm1, cm2, cm3=cm3)

which behaves as the same as

with cm1 as cm1_, cm2 as cm2_, cm3 as cm3_:
    ret = some_function(cm1_, cm2_, cm3=cm3_)

By the way, if you are concerned when writing

from glob import glob
jsons = [
    json.load(open(fname))
    for fname in glob("./*.json")
]

, you can also write the following

from glob import glob
jsons = [
    owith(json.load, open(fname))
    for fname in glob("./*.json")
]

2nd function: owith_all(func: typing.Callable) -> typing.Callable

When writing

def func(cm):
    with cm as cm_:
        return True

, you can alternatively write

@owith_all
def func(cm):
    return True

with owith_all decorator.

3rd function: dcwith(*args) -> Callable[[typing.Callable, ], typing.Callable]

When writing

def func():
    return True

with cm1, cm2, ..., cmN:
    func()

, you can alternatively write

def func():
    return True

dcwith(cm1, cm2, ..., cmN)(func)()

or

@dcwith(cm1, cm2, ..., cmN)
def func():
    return True

func()

with dcwith.

Effectiveness and Efficiency

Let us see the impact of OWith on your python codes using three example.

Assume that import json have been already executed in the following examples.

First Example

The following python scripts are funcionally equivalent:

with open("sample.json") as f:
    dic = json.load(f)

and

ret = owith(json.load, open("sample.json"))

But the number of characters in the former is 52 while that in the latter is 43. That is, owith reduce the number of characters by 9.

Second Example

The following python scripts are functionally equivalent:

def jload(file_obj):
    with file_obj as f:
        return json.load(f)

and

@owith_all
def jload(file_obj):
    return json_load(file_obj)

But the number of characters in the former is 70 while that in the latter is 60. That is, owith_all reduce the number of characters by 10.

Thrid Example

The following python scripts are functionally equivalent:

def func():
    return True

with stopwatch_cm:
    func()

and

@dcwith(stopwatch_cm)
def func():
    return True

func()

But the number of characters in the former is 54 while that in the latter is 53. That is, dcwith reduce the number of characters by 1.

Contribution Guide

Requirement

  • python >= 3.7
  • pipenv

Setup

$ git clone https://github.com/hmasdev/owith.git
$ cd owith
$ pipenv install --dev

Issues

  • For any bugs, use BUG REPORT to create an issue.

  • For any enhancement, use FEATURE REQUEST to create an issue.

  • For other topics, create an issue with a clear and concise description.

Pull Request

  1. Fork (https://github.com/hmasdev/owith/fork);
  2. Create your feature branch (git checkout -b feautre/xxxx);
  3. Test codes according to Test Subsection;
  4. Commit your changes (git commit -am 'Add xxxx feature);
  5. Push to the branch (git push origin feature/xxxx);
  6. Create new Pull Request

Test

$ pipenv run flake8
$ pipenv run mypy .
$ pipenv run pytest

LICENSE

MIT

Authors

hmasdev