Libraries like giambio shine the most when it comes to performing asyncronous I/O (reading a socket, writing to a file, that sort of thing).
The most common example of this is a network server that needs to handle multiple connections at the same time.
One possible approach to achieve concurrency is to use threads, and despite their bad reputation in Python, they
actually might be a good choice when it comes to I/O for reasons that span far beyond the scope of this tutorial.
If you choose to use threads, there are a couple things you can do, involving what is known as _thread synchronization
primitives_ and _thread pools_, but once again that is beyond the purposes of this quickstart guide.
A library like giambio comes into play when you need to perform lots of [blocking operations](https://en.wikipedia.org/wiki/Blocking_(computing)
and network servers, among other things, happens to rely heavily on I/O which is a blocking operation.
Starting to see where we're heading?
## A deeper dive
giambio has been designed with simplicity in mind, so this README won't explain all the gritty details about _how_ async is
implemented in Python (you might want to check out [this article](https://snarky.ca/how-the-heck-does-async-await-work-in-python-3-5/) if you want to learn more about all the implementation details).
For the sake of this tutorial, all you need to know is that functions defined giambio is all about a feature added in Python 3.5:
asynchronous functions, or 'async' for short.
Async functions are functions defined with `async def` instead of the regular `def`, like so:
```python
async def async_fun(): # An async function
print("Hello, world!")
def sync_fun(): # A regular (sync) function
print("Hello, world!")
```
First of all, async functions like to stick together: to call an async function you need to put `await` in front of it, like below:
```python
async def async_two():
print("Hello from async_two!")
async def async_one():
print("Hello from async_one!")
await async_two() # This is an async call
```
It has to be noted that using `await` outside of an async function is a `SyntaxError`, so basically async
functions have a unique superpower: they can call other async functions. This already presents a chicken-and-egg
problem, because when you fire up Python it is running plain ol' synchronous code, so how do we enter the async
context in the first place? That is done via a special _synchronous function_, `giambio.run` in our case,
that has the ability to call asynchronous functions and can therefore initiate the async context. For this
reason, `giambio.run`**must** be called from a synchronous context, to avoid a horrible _deadlock_. Now
that you know all of this, you might be wondering why on earth would one use async functions instead of
regular functions: after all, their ability to call other async functions seems pretty pointless in itself, doesn't it?
Take a look at this example below:
```python
import giambio
async def foo():
print("Hello, world!")
giambio.run(foo) # Prints 'Hello, world!'
```
This could as well be written the following way and would produce the same output:
```python
def foo():
print("Hello, world!")
foo() # Prints 'Hello, world!'
```
To answer this question, we have to dig a bit deeper about _what_ giambio gives you in exchange for all this `async`/`await` madness.
We already introduced `giambio.run`, a special runner function that can start the async context from a synchronous one, but giambio
provides also a set of tools, mainly for doing I/O. These functions, as you might have guessed, are async functions and they're useful!
So if you wanna take advantage of giambio, and hopefully you will after reading this guide, you need to write async code.
As an example, take this function using `giambio.sleep` (`giambio.sleep` is like `time.sleep`, but with an async flavor):
__Side note__: If you have decent knowledge about asynchronous python, you might have noticed that we haven't mentioned coroutines
so far. Don't worry, that is intentional: giambio never lets a user deal with coroutines on the surface because the whole async
model is much simpler if we take coroutines out of the game, and everything works just the same.
```python
import giambio
async def sleep_double(n):
await giambio.sleep(2 * n)
giambio.run(sleep_double, 2) # This hangs for 4 seconds and then returns
