add = lambda x, y: x + y
print(add(2, 3)) # 5
print(add("hello", "world!")) # helloworld

names = [ 'David Beazley', 'Brian Jones', 'Reymond Hettinger', 'Ned Batchelder']
sorted_names = sorted(names, key=lambda name: name.split()[-1].lower())
print(sorted_names)
# ['Ned Batchelder', 'David Beazley', 'Reymond Hettinger', 'Brian Jones']

x = 10
a = lambda y: x + y 
x = 20
b = lambda y: x + y

x = 10
a = lambda y, x=x: x + y
x = 20
b = lambda y, x=x: x + y
print(a(10)) # 20
print(b(10)) # 30

funcs = [lambda x: x + n for n in range(5)]
for f in funcs:
    print(f(0))
# 4
# 4
# 4
# 4
# 4

funcs = [lambda x, n=n: x + n for n in range(5)]
for f in funcs:
    print(f(0))
# 0
# 1
# 2
# 3
# 4

functools.partial(func, /, *args, **keywords)

def spam(a, b, c, d):
  print(a, b, c, d)

from functools import partial
s1 = partial(spam, 1) # 設(shè)定好a = 1（如果沒(méi)指定參數(shù)名，默認(rèn)按順序設(shè)定）
s1(2, 3, 4) # 1 2 3 4

s2 = partial(spam, d=42) # 設(shè)定好d為42
s2(1, 2, 3) # 1 2 3 42

s3 = partial(spam, 1, 2, d=42) #設(shè)定好a = 1, b = 2, d = 42
s3(3) # 1 2 3 42

points = [(1, 2), (3, 4), (5, 6), (7, 8)]

import math
def distance(p1, p2):
    x1, y1 = p1
    x2, y2 = p2
    return math.hypot(x2 - x1, y2 - y1)

pt = (4, 3)
points.sort(key=partial(distance, pt)) # 先指定好一個(gè)參數(shù)為pt=(4，3)
print(points)
# [(3, 4), (1, 2), (5, 6), (7, 8)]

pt = (4, 3)
points.sort(key=lambda p: distance(p, pt))
print(points)
# [(3, 4), (1, 2), (5, 6), (7, 8)]

pt = (4, 3)
func_key = lambda p: distance(p ,pt) 
pt = (0, 0) # 像這樣，后面pt變了就GG
points.sort(key=func_key)
print(points)
# [(1, 2), (3, 4), (5, 6), (7, 8)]

# result：回調(diào)函數(shù)本身該接受的參數(shù), log是我想使其擴(kuò)展的參數(shù)
def output_result(result, log=None):
    if log is not None:
        log.debug('Got: %r', result)

def add(x, y):
    return x + y

if __name__ == '__main__':
    import logging
    from multiprocessing import Pool
    from functools import partial
    logging.basicConfig(level=logging.DEBUG)
    log = logging.getLogger('test')
    p = Pool()
    p.apply_async(add, (3, 4), callback=partial(output_result, log=log))
    p.close()
    p.join()

# DEBUG:test:Got: 7

from socketserver import StreamRequestHandler, TCPServer
class EchoHandler(StreamRequestHandler):
    def handle(self):
        for line in self.rfile:
            self.wfile.write(b'GoT:' + line)

serv = TCPServer(('', 15000), EchoHandler)
serv.serve_forever()

class EchoHandler(StreamRequestHandler):
    def __init__(self, *args, ack, **kwargs):
        self.ack = ack
        super().__init__(*args, **kwargs) 
    def handle(self) -> None:
        for line in self.rfile:
            self.wfile.write(self.ack + line)

from functools import partial
serv = TCPServer(('', 15000), partial(EchoHandler, ack=b'RECEIVED'))
serv.serve_forever()

def apply_async(func, args, *, callback):
    # 計(jì)算結(jié)果
    result = func(*args)
    # 將結(jié)果傳給回調(diào)函數(shù)
    callback(result)

# 要回調(diào)的函數(shù)
def print_result(result):
    print("Got: ", result)
    
def add(x, y):
    return x + y

apply_async(add, (2, 3), callback=print_result)
# Got: 5
apply_async(add, ('hello', 'world'), callback=print_result)
# Got: helloworld

class SequenceNo:
    def __init__(self) -> None:
        self.sequence = 0

def handler(result, seq):
    seq.sequence += 1
    print("[{}] Got: {}".format(seq.sequence, result))

seq = SequenceNo()
from functools import partial
apply_async(add, (2, 3), callback=partial(handler, seq=seq)) 
# [1] Got: 5
apply_async(add, ('hello', 'world'), callback=partial(handler, seq=seq))
# [2] Got: helloworld

class ResultHandler:
    def __init__(self) -> None:
        self.sequence = 0
    def handler(self, result):
        self.sequence += 1
        print("[{}] Got: {}".format(self.sequence, result))

apply_async(add, (2, 3), callback=r.handler) 
# [1] Got: 5
apply_async(add, ('hello', 'world'), callback=r.handler) 
# [2] Got: helloworld

def make_handler():
    sequence = 0
    def handler(result):
        nonlocal sequence # 在閉包中編寫(xiě)函數(shù)來(lái)修改內(nèi)層變量，需要用nonlocal聲明
        sequence += 1
        print("[{}] Got: {}".format(sequence, result))
    return handler

handler = make_handler()
apply_async(add, (2, 3), callback=handler) 
# [1] Got: 5
apply_async(add, ('hello', 'world'), callback=handler) 
# [2] Got: helloworld

def make_handler_cor():
    sequence = 0
    while True:
        result = yield
        sequence += 1
        print("[{}] Got: {}".format(sequence, result))

handler = make_handler_cor()
next(handler) # 切記在yield之前一定要加這一句
apply_async(add, (2, 3), callback=handler.send) #對(duì)于協(xié)程來(lái)說(shuō)，可以使用它的send()方法來(lái)做為回調(diào)函數(shù)
# [1] Got: 5
apply_async(add, ('hello', 'world'), callback=handler.send)
# [2] Got: helloworld