Quickstart - Backend¶

Installation¶

sudo pip install izzati

Usage¶

A simple example which prints out the data received and a list of the filenames of all the files which were received.

from izzati import Backend, file_return

def p(text, data):
    print(text, [x.filename for x in data])
    return {'status': 'yes'}
    # return file_return('file.txt')

b = Backend(p)
b.run() # The host and port can be set as well:
# b.run(host='0.0.0.0', port=5030) # Default is 0.0.0.0 and 5020

The function must have arguments for text and data, even if no data is sent.

A file can also be returned with the file_return function.

Data¶

The data supports many functions that are revealed:

file.read() Read a file file.save(location) Save a file to a location file.filename The name of the file when it was transferred

Text¶

The text is all returned as a dictionary, with keys and values. During transit, it is converted to JSON, but will always be exposed as a dictionary.

Background Processes¶

Izzati provides a nice frontend for background processes and supports running the backend in the background or a function in the background. This is built on top of multiprocessing and supports multiple CPU cores etc.

Make the webserver in the background.

from izzati import Backend

def callback(q, text, data): # <---------------------------------
    print(text, [x.filename for x in data])
    return {'status': 'OK'}

b = Backend(callback, background=True) # <-----------------------
p, q = b.run() # <----------------------------------------
# Block the Python process, or else everything quits

Notice there’s two extra return values, p and q and the callback accepts an extra argument. This is a Queue object, where you can communicate with the callback function. Use q.put("hello") to put data into the queue and q.get() to get data out of the queue. p is the process, which can be used to join (p.join()) or to kill etc.

See https://docs.python.org/3/library/multiprocessing.html for more details.

The callback, in this case, must have q as the first argument, with no default value.

Make another process in the background.

from izzati import Backend, background # <-------------

def callback(text, data, q):
    print(text, [x.filename for x in data])
    q.put(text['name'])
    return {'status': 'OK'}

def background_process(q, greeting): # <---------------
    while True:
        name = q.get()
        print(greeting + ", " + name)

p, q = background(background_process, args=("Hello",)) # <--------------
# Also supports default arguments with kwargs:
# p, q = background(background_process, kwargs={"greeting": "Hello"})

b = Backend(callback, args=(q,)) # <-----------------------
# Also supports default arguments with kwargs:
# b = Backend(callback, kwargs={'q': q})

b.run()

These methods can be used at the same time as well, but something must be blocking the Python code from finishing.

Arguments¶

The Backend object supports args and kwargs, as shown above. The background process does as well. In both, the args and kwargs follow the essentials, such as text, data, and q if running in the background.