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python学习心得

一,高级特性:

1,切片:[start:stop:step]

>>>l=range(6)
>>>l[3,-1,2]
resulte is [3]

2,迭代

  2.1按itervalues()

>>> d={1:2,2:3,3:4}
>>> for k in d:
...     print k,d[k]
... 
1 2
2 3
3 4

  2.2 按iteritems()

>>> for v in d.iteritems():
...     print v
... 
(1, 2)
(2, 3)
(3, 4)
以元组形式返回

  2.3 带索引输出:enumerate

>>> for i,value in enumerate([a,b,c]):
...     print i,value
... 
0 a
1 b
2 c

  2.4 生成器:一边循环一边计算的机制,称为生成器(Generator),有利于节省存储空间,相当于链表中next

>>> def fib(max):
...     n,a,b=0,0,1
...     while n<max:
...             yield b
...             a,b=b,a+b
...             n=n+1
... 
>>> fib(6)
<generator object fib at 0x7f7f3c2b94b0>
>>> for i in fib(6):
...     print i
... 
1
1
2
3
5
8

(二),函数式编程

1,高阶函数:函数名当作方法的参数变量

>>> def add(x,y,abs):
...     return abs(x)*abs(y)
>>> def cut(x,add):
...     return x-add(x,x,abs)
... 
>>> cut(1,add)
0

2,map

把用户输入的不规范的英文名字,变为首字母大写,其他小写的规范名字
map(lambda s :s.capitalize(),[AC,ac]
[Ac,Ac]

reduce:

>>> l=map(lambda s:s.capitalize(),[AC,ac])
>>> reduce(lambda x,y:x+y,l)
AcAc

filter:

>>> import math
>>> def isPrim(s):
...     for i in range(2,int(math.sqrt(s)+1)):
...             if s%i==0:
...                     return False
...     return True
... 
>>> filter(isPrim,range(2,10))
[2, 3, 5, 7]
>>> import time
>>> print time.mktime(time.localtime())//时间计算
1497605034.0

 3,sorted  x>y 1,x<y -1 x==y 0

 sorted([1,3,2],lambda x,y:y-x) //如果y-x>0则两个数交换位置,使用冒泡排序
[3, 2, 1]

4,闭包(Closure),使用返回函数形式:

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

5,匿名函数:lambda

6,“装饰器”(Decorator):对方法进行增强说明,但有不去改变方法

import functools

def log(args):
    """"""
    task = "call"
    def actual_log(func):
        @functools.wraps(func)
        def wrapper(*args,**kw):
            print %s:%s() % (task,func.__name__)//两个下划线
            return func(*args, **kw)
        return wrapper
    if hasattr(args,__call__):
        return actual_log(args)
    else:
        task = args
        return actual_log

@log
def f():
    pass

@log("execute")
def e():
    pass

5,偏函数

>>> max2=functool.partial(max,10) //10作为*args的一部分自动加到左边
>>> max2(1,3,4,5)
10
>>> def func(a,b,c):
>>>  print a,b,c
>>>func2=functools.partial(func,b=3) 替换关键参数
>>>func(1,c=4)
1 3 4

 

python学习心得