chapter7 函数式编程

闭包 匿名函数 装饰器 偏函数

##closure
#
def calc_sum(*args):
    ax = 0
    for n in args:
        ax += n
    return ax

def lazy_sum(*args):
    def sum():
        ax = 0
        for n in args:
            ax += n
        return ax
    return sum

f = lazy_sum(1, 3, 5, 7, 9)
print(f)
print(f())


def count():
    fs = []
    for i in range(1, 4):
        def f():
            return i*i
        fs.append(f)
    return fs


f1, f2, f3 = count()

print(f1(), f2(), f3())


def count():
    def f(j):
        def g():
            return j * j
        return g
    fs = []
    for i in range(1, 4):
        fs.append(f(i))  #f(i)立刻被执行
    return fs

f1, f2, f3 = count()
print(f1(), f2(), f3())


def createCounter():
    num = 0
    def counter():
        nonlocal num    
        num += 1
        return num
    return counter

f = createCounter()
print(f())
print(f())
f2 = createCounter()
print(f2(), f2(), f2())


##lambda
#
print(list(map(lambda x: x * x, [1, 2, 3, 4, 5, 6, 7, 8, 9])))

f = lambda x : x * x
print(f)


def build(x, y):
    return lambda: x * x + y *y

print(build(1, 3)())

##用匿名函数改造
def is_odd(n):
    return n % 2 == 1
L1 = list(filter(is_odd, range(1, 20)))
L2 = list(filter(lambda n : n % 2 == 1, range(1, 20)))

print('?', L1, L2)


##decorator
#
def now():
    print('2015-3-25')

f = now
print(f())

print(now.__name__)
print(f.__name__)


def log(func):
    def wrapper(*args, **kw):
        print('call %s():' % func.__name__)
        return func(*args, **kw)
    return wrapper

@log
def now():
    print('2015-3-25')

now()

##更复杂的decorator

def log(text):
    def decorator(func):
        def wapper(*args, **kw):
            print('%s %s():' % (text, func.__name__))
            return func(*args, **kw)
        return wapper
    return decorator

@log('excute')
def now():
    print('greater:', '2015-3-25')

now()

print(now.__name__)

##更好的decorator
import functools


def log(text):
    def decorator(func):
        @functools.wraps(func)
        def wapper(*args, **kw):
            print('%s %s():' % (text, func.__name__))
            return func(*args, **kw)
        return wapper
    return decorator


@log('excute')
def now():
    print('greater:', '2015-3-25')


print(now.__name__)

##练习
import time
import functools
def time_decorator(func):

    @functools.wraps(func)
    def wapper(*args, **kw):
        now_mills = time.time() * 1000
        print('%s executed in %s ms' % (func.__name__, now_mills))
        return func(*args, **kw)

    return wapper

@time_decorator
def any_func(*c):
    temp = [str(s) + '!'  for s in c ]
    print(type(temp))
    print('hello:', temp)
    

any_func(('Alice', 'Aha'))


print(any_func.__name__)

##Partial function 
#
print(int('01234'))
print(int('1234', base = 8))

def int2(x):
    return int(x, base = 2)
print(int2('10000'))

print(int('10000', 2))

import functools

int2 = functools.partial(int, base = 2)

print(int2('100000'))


max2 = functools.partial(max, 10)
print(max2(1, 2, 3, 9))