python 基础2

# encoding=utf-8from math import sqrtif __name__==('__main__'):    #序列解包    x,y,z=1,2,3    print x,y,z    x = ['gjl','xff','ccc']    y = ['gjj','xoo','cee']    print [(a,b) for a in x for b in y if a[0] == b[0]]    letterys = {}    for a in x:            letterys.setdefault(a[0],[]).append(a)    print letterys    print( [(a,b) for a in x for b in letterys[a[0]]])    #循环中的else子句 注意他仅在没有执行break 句子的时候执行    """    while True:        name = raw_input('please input your name:')        if name:            print('your name is '+name)            break    """    for x in range(99,0,-1):        root = sqrt (x)        if root == int (root):            print root            break    else:        print('dint find it')    #抽象 参数 作用域    fibs = [0,1]    for x in range(10):        f = fibs[-2]+fibs[-1]        fibs.append(f)    print fibs    def try_to_change(n):        n[0] = 's'    name = ['mr','s']    try_to_change(name)    print name    #关键字参数和默认值 关键字参数就是使用参数名 来调用参数 这样使得每个参数具有集体的意义    def saysomething(name,greeting):        print( greeting+','+name)    saysomething(greeting='hello',name='gjl')    #很多时候可以让用户输入任意多的参数是非常有用的 可以 用* 支持  用** 支持关键字参数的收集    def print_params(**paras):        print paras    print_params(name ='a',gr='b')    #输出{'name': 'a', 'gr': 'b'}    #s收集参数的逆过程    def add(x,y):        return x+y    print add(*(1,2))    params ={        'name':'gjl',         'greeting':'hello'}    saysomething(**params)    #下面的函数是对之前多讲的练习 主要是对于关键字参数的把握 以及参数收集 总体记住一点 *（**）可以传递元组 字典    def power(x,y,*others):        if others:            print 'redudunt paramters'        return pow(x,y)    def interval(start,stop=None,step=1):        if stop is None:            start,stop=0,start        result = []        for x in range(start,stop,step):            result.append(x)        return result    def sayHello(**kwds):        print '%(greeting)s you are %(name)s are you ' % kwds    sayHello(**{'greeting':'hello',              'name':'gjl'})    print power(*(2,3))    power(2,3,'hello')    print power(x=2,y=3)    print interval(0,10,2)    print interval(10)    #嵌套作用域 python中 函数是可以嵌套的 嵌套函数有一个很突出的作用 就是利用函数创建函数 下面的被创建的函数就可以访问 创建函数 的 参数，    # 类似 被创建函数 存储子作用域的行为 叫做 closure    #    def multiplier(factor):        def mutiplyByFactor(numbers):            return numbers*factor        return mutiplyByFactor    double = multiplier(2)    print(double(3))    #递归recursion 阶乘 幂    def recn(n):        if n==0:            return 1        return n*recn(n-1)    print 102,recn(3)    def power1(x,y):        if y ==1:            return x        return x*power1(x,y-1)    print 107, power1(2,3)    #二分查找的基本要求是 列表有序    def search(lower,upper,x,seq):        if(lower == upper):            if (seq[upper]==x):                return upper            else:return None        mid =(upper +lower)/2        if(x>seq[mid]):            return search(mid+1,upper,x,seq)        else:            return search(lower,mid,x,seq)    l =[1,2,4,5,7]    print 120,search(0,len(l)-1,9,l)    #利用关键字参数改写    def searchNew(x,seq,lower=0,upper=None):        if upper is None:            upper = len(seq)-1        if(lower == upper):            if (seq[upper]==x):                return upper            else:return None        mid =(upper +lower)/2        if(x>seq[mid]):            return searchNew(x,seq,mid+1,upper)        else:            return searchNew(x,seq,lower,mid)    print 136, searchNew(1,l)