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这篇文章主要介绍Python生成器、装饰器、递归的示例分析,文中介绍的非常详细,具有一定的参考价值,感兴趣的小伙伴们一定要看完!
1、Python生成器表达式
1)、Python生成器表达式
语法格式:
(expr for iter_var in iterable)
(expr for iter_var in iterable ifcond_expr)
2)、自定义生成器
函数中使用yield,会返回一个生成器对象。yieldx
生成器使用示例:
In [1]:list((i**2 for i in range(1,11))) Out[1]:[1, 4, 9, 16, 25, 36, 49, 64, 81, 100] In [2]:def genNum(x): ...: y = 0 ...: while y <= x: ...: yield y ...: y += 1 In [3]: g1= genNum(4) In [4]:type(g1) Out[4]:generator In [5]:g1.next() Out[5]:0 In [6]:g1.next() Out[6]:1 In [7]:g1.next() Out[7]:2 In [8]:g1.next() Out[8]:3 In [9]:g1.next() Out[9]:4 In [10]:g1.next() -------------------------------------------------- StopIteration Traceback (most recent call last) in() ----> 1g1.next() StopIteration: In [11]:def genNum(n): ....: i = 1 ....: while i <= n: ....: yield i ** 2 ....: i += 1 In [12]:g1 = genNum(20) In [13]:for i in g1: ....: print i, ....: 1 4 9 1625 36 49 64 81 100 121 144 169 196 225 256 289 324 361400
2、Python装饰器
1)、装饰器本身是一个函数,用于装饰其它函数;
2)、功能:增强被装饰函数的功能;
装饰器一般接受一个函数对象作为参数,以对其进行增强
例1:装饰器使用示例
In [1]:def decorater(func): ...: def wrapper(): ...: print "Just a Decorater!" ...: func() ...: raw_input('Please Input your name:') ...: return wrapper ...: In [2]:@decorater ...:def show(): ...: print "I am from China." ...: In [3]:show() Just aDecorater! I am fromChina. PleaseInput your name:Fieldyang
例2:对能够传入参数的函数进行装饰
In [1]:def decorater(func): ...: def wrapper(x): ...: print "Just a Decorater!" ...: func(x) ...: raw_input('Please Input your name:') ...: return wrapper ...: In [2]:@decorater ...:def show(x): ...: print "I am from China.%s" %x ...: In [3]:show('how are you ?') Just aDecorater! I am fromChina.how are you ? PleaseInput your name:Fieldyang
3、Python递归
递归需要边界条件,递归前进段和递归返回段;
10 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 *1 10 * (10-1)* ((10-1)-1)* ...
递归函数使用示例:
In [1]:def recursion(n): ...: if n <= 1: return 1 ...: else: return n * recursion(n-1) ...:
#递归函数相当于如下过程:
In [2]: recursion(3) = 3 * recursion(2)= 3 * 2 *recursion(1)=3*2*1 KeyboardInterrupt In [3]:recursion(3) Out[3]:6 In [4]:recursion(4) Out[4]:24 In [5]:recursion(5) Out[5]:120 In [6]:recursion(10) Out[6]:3628800
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