Python生成器、装饰器、递归

ゝ一世哀愁。 2022-05-23 08:48 90阅读 0赞

**Python生成器、装饰器、递归**

**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

Python生成器、装饰器、递归

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