Python_day6

　　　Δ汉诺塔例子

# 定义三个全局的列表
la = []
lb = []
lc = []

stepn = 0

def create_hano(n):
    '''构建由n个圆盘组成的汉诺塔'''
    global la
    la = [i for i in range(n, 0, -1)]    


def move(src, dest):
    '''从src柱子上最上面的圆盘移动到dest柱子上'''
    dest.append(src.pop())
    global stepn    
    stepn += 1

    input()

    print('柱子A:',la)
    print('柱子B:',lb)
    print('柱子C:',lc)


def start_game(src, tmp, dest, n):
    if n == 1:
        move(src, dest)
        return None
    if n < 1:
        return -1
    start_game(src, dest, tmp, n-1)    
    start_game(src, tmp, dest, 1)
    start_game(tmp, src, dest, n-1)


create_hano(4)
print('柱子A:',la)
print('柱子B:',lb)
print('柱子C:',lc)
start_game(la, lb, lc, 4)
print(stepn)

• 生成器(generator):
• 迭代器(Iterator):

　　　　　　next()得到成员的:generator

• 可迭代(Iterable):

　　　　能用for遍历的:str, list, tuple, dict, set, generator, range
　　　　collections模块中定义的Iterator和Iterable类型

# 从1开始的fib
def fib(n):
    a, b = 0, 1
    while n > 0:
        # print(b)
        yield b # 随着生成器调用next方法，得到yield的值
        a, b = b, a+b
        n -= 1
    return 'done'

g = fib(10)
print(g)

• 匿名函数 lambda : 适合函数功能简洁的

f = lambda x : True if x % 2 == 0 else False
print(type(f))

print(f(101))

f = lambda : print('hello world')
f()

f = lambda x, y : x * y
print(f(10, 14))

f = lambda x, y=2 : x ** y
print(f(5, 5))

f = lambda x, *arg : print(x, arg) 
print(f(1, 2,3,4,5,6))

• 高阶函数：函数为参
• map()：对多个参数进行同一操作

  def test(n):
      return n ** 3
  
  # g = map(test, (1,2,3,4))
  g = map(lambda x : x**3, (1,2,3,4))
  print(type(g))
  
  print(next(g))
  print(next(g))
  print(next(g))
  
  '''
  for res in g:
      print(res)
  '''
  l = list(g)
  print(l)

  '''
  练习1:
      生成一个由5个10以内随机整型数组成的列表，使用高阶函数map实现将5个整型数分别转换为字符串
  '''
  import random
  
  l = [random.randrange(10) for i in range(5)]
  print(l)
  l = list(map(str, l))
  print(l)
  
  '''
  练习2:
      将列表中每一个元素都转换为一个标准的标题，首字符大写其它小写
          l = ['hello world', 'Good AFTERNOON', 'morning']
  '''
  l = ['hello world', 'Good AFTERNOON', 'morning']
  l = list(map(lambda x : x.title(), l))
  print(l)

• filter()：过滤

  res = filter(lambda x : x % 2 == 0, [random.randrange(100) for i in range(10)])
  print(list(res))

• sorted()：排序，有key值默认为NONE

  l = ['hello', 'Yes', 'PYTHON', 'world', 'Go']
  res = sorted(l, key=str.lower, reverse=True) # 按小写排序
  print(res)

• reduce() :两个变量后跟类型  functools

from functools import reduce

def f(x, y):
    return x * 10 + y

n = reduce(f, (1,5,6,7))
print(type(n), n)

n = reduce(lambda x,y : x*y, (1,2,3,4,5,6))
print(n)

'''
实现一个将字符串转换为整型数的函数str2int()
    '1432' ----> 1432 不允许调用int函数
'''
def str2int(s):
    g = map(lambda x:ord(x)-ord('0'), s)
    return reduce(lambda x, y:x*10+y, g)

print(str2int('1423'))

• 装饰器(decorator):修饰函数

 

import datetime
d = datetime.date()
print(d)
'''
# 函数作为返回值
def test():
    return str

f = test()
print(f(1234))

import functools

def decorator(f):
    @functools.wraps(f) # 此装饰器作用是将f的函数名赋值给wrapper
    def wrapper(*args, **kw):
        '''装饰器的内部函数'''
        # print(args, kw)
        print('hello python')
        # print(f.__name__)
        return f(*args, **kw)
    return wrapper

@decorator 
def show(name1, name2):
    '''验证装饰器功能的小函数'''
    print('hello %s and %s' % (name1, name2))
    return 100

print(show.__name__)
print(show.__doc__)
res = show('aa', 'bb') # show = decorator(show)
print(res)

　　带参数的装饰器

import functools

def log(text, text2):
    def decorator(f):
        @functools.wraps(f)
        def wrapper(*args, **kw):
            print('log', text, text2)    
            print('这个装饰器好吧?')
            return f(*args, **kw)
        return wrapper
    return decorator


@log('argument', 'haha')
def now():
    print('2018-12-12')

now() # now = log('argument')(now)