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creature-0.1.17
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-
| ویژگی | مقدار |
|---|---|
| سیستم عامل | - |
| نام فایل | creature-0.1.17 |
| نام | creature |
| نسخه کتابخانه | 0.1.17 |
| نگهدارنده | [] |
| ایمیل نگهدارنده | [] |
| نویسنده | pwtail |
| ایمیل نویسنده | abvit89s@gmail.com |
| آدرس صفحه اصلی | - |
| آدرس اینترنتی | https://pypi.org/project/creature/ |
| مجوز | - |
# creature
## Intro
This library demonstrates the use of **greenlet as a bridge to async
code**. It makes the code written for blocking I/O able to work with async I/O.
An example can be an ORM that previously used blocking
database drivers and
starts using an async database driver.
Actually, it was not intended as a demo from the start, it was intended to be
used in production, therefore the code quality is good. Actually, I have
written an
async
django database [backend](https://github.com/Bi-Coloured-Python-Rock-Snake/pgbackend) using it.
The same approach is used by sqlalchemy to provide its async features. However,
this library is more advanced in terms of features as it **provides support
for REPL, context managers, iterators, context vars**.
However, I decided to discontinue it. The thing is there are two approaches to
async programming: one uses
the "colored
functions" approach (a term first used in a [post](
https://journal.stuffwithstuff.com/2015/02/01/what-color-is-your-function/)
by Bob Nystrom),
and the other one does not. A vivid example is **Python vs. Ruby**: Python
coroutines are colored and Ruby Fibers (appeared in 1.9) are not.
As you can
see, this repository is placed in the "Bi-Coloured-Python-Rock-Snake" group.
When I titled it that way, I considered function colors a bad thing, however I
have come to a conclusion that the matter of things is far from
unambiguity. There
are many nuances to this but shortly speaking, I embraced the **Python way of
things**.
Still, the library can be a nice demo of what sqlalchemy is doing under the
hood. The name is a tribute
to sqlalchemy.
## Description
This library makes it possible for the regular (sync-looking) functions to have
async
implementation under the hood.
It does that by using
[greenlet](https://github.com/python-greenlet/greenlet).
The main principle is to separate sync and async code by two different
greenlets. Then, all async tasks are being sent to the async greenlet and
executed there,
while the sync greenlet doesn't do any I/O itself.
## Install
```
pip install creature
```
## Usage
You can turn an async function into a sync one by using `exempt` decorator:
```python
from creature import exempt
@exempt
async def sleep(secs):
await asyncio.sleep(secs)
print(f'Slept for {secs} seconds')
@exempt
async def download(url):
async with httpx.AsyncClient() as client:
resp = await client.get(url)
print(f'Downloaded {len(resp.content)} bytes')
```
"Exempt" means that coroutines are exempted from the current greenlet, and
sent to another.
Now, to call those functions you have two options:
**1. as_async decorator**
You can use `as_async` decorator to make the main function async again and
run it with an event loop:
```python
from creature import as_async
@as_async
def main():
sleep(0.5)
download('https://www.python.org')
asyncio.run(main())
```
Which will print
```commandline
Slept for 0.5 seconds
Downloaded 50856 bytes
```
**2. start_loop()**
You can also start an event loop yourself - this may be useful for interactive
use or scripts.
```python
import creature
creature.start_loop()
sleep(0.5)
download('https://www.python.org')
```
Which will print the same.
**The REPL**
start_loop() doesn't work in IPython REPL. It works in the PyCharm Console
though.
The reason is that IPython starts the asyncio loop itself. The
prompt_toolkit used by IPython, also needs an async loop.
So, for IPython there
is a
different solution:
```python
import creature
creature.ipy.enable()
```
This works in both PyCharm Console and IPython.
**Context vars**
asyncio has `contextvars` module that gives coroutines access to their
"context". creature has its own contextvars for the very same purpose.
greenlet itself has support for contextvars: all greenlets have different
contexts.
However, as you should know by now, we have two
greenlets, sync and async, and it's natural for them to share the context.
The class intentionally is called context_var, not to import the standard
ContextVar by mistake.
```python
creature.start_loop()
var = creature.context_var(__name__, 'var', default=-1)
@exempt
async def f1():
# set() returns the previous value
assert var.set(1) == -1
def f2():
assert var.get() == 1
f1()
f2()
```
As you can see, sync and async functions can use shared context.
**Context managers**
Functions are not the only thing you can come across, sometimes you have to
deal with context managers too. creature can map async context managers to the
sync ones. Here is how it is done:
```python
@exempt_cm
@asynccontextmanager
async def have_rest(before, after):
await asyncio.sleep(before)
try:
yield
finally:
await asyncio.sleep(after)
with have_rest(1, 3):
print('Party!')
```
`exempt_cm` stays for "exempt the context manager", of course. This feature
had been
useful when I
was working on the async backend for django, because the psycopg3 driver
uses context managers extensively.
**Iterators**
You get the principle, don't you? Similarly, we have `exempt_it` for iterators.
```python
@exempt_it
async def counter():
for i in range(3):
await asyncio.sleep(0.1 * i)
yield i
assert list(counter()) == [0, 1, 2]
```
نیازمندی
| مقدار | نام |
|---|---|
| >=2.0.1,<3.0.0 | greenlet |
زبان مورد نیاز
| مقدار | نام |
|---|---|
| >=3.10,<4.0 | Python |
نحوه نصب
نصب پکیج whl creature-0.1.17:
pip install creature-0.1.17.whl
نصب پکیج tar.gz creature-0.1.17:
pip install creature-0.1.17.tar.gz