pipes in python

fun.py

import urllib.request as rq

class ConfusedThreader(Exception):
    pass

class Fun:
    def __getattr__(self,attribute):
        def aux(o):
            return getattr(o,attribute)()
        return aux

fn = Fun()
done = lambda t: t.val()

class Threader:
    def __init__(self, v):
        self.v = v
        self.fns = []

    def val(self):
        r = self.v
        for f in self.fns:
            r = f(r)
        return r

    def __or__(self,other):
        if other is done:
            return done(self)
        elif callable(other):
            self.fns.append(other)
            return self
        elif other is None:
            return self.val()
        else:
            raise ConfusedThreader()

class DebuggingThreader(Threader):

    def __init__(self, v, verbose=True):
        super().__init__(v)
        self.verbose = verbose
        self.trace = {}

    def val(self):
        r = self.v
        for f in self.fns:
            try:
                o = r
                r = f(r)
                self.trace[f] = (o, r)
                if self.verbose:
                    print('[debug]',f,o,r)
            except Exception as e:
                print(e)
        return r
    
def Thread(o, debug=False):
    return DebuggingThreader(o) if debug else Threader(o)

DEBUG=True

def demo():
    Thread("https://www.example.com",DEBUG) \
    | rq.urlopen \
    | fn.readlines \
    | b''.join \
    | fn.decode \
    | print \
    | done