Python语法基础（四）

捕获异常

a = 10
try:
    a / 0
except:
    print("error")

迭代器

#迭代器，往前访问元素
list_ = [1,2,3,4]

it = iter(list_)
'''
for x in it:
    print(x,end="..")
'''

while True:
    try:
        print (next(it))
    except:
        break

#生成器 
#普通输出斐波那契数列
def fab(max):
    n , a, b = 0, 0, 1
    while n<max:
        print(b)
        a ,b = b ,a+b
        n = n+1
            
fab(6)


#提高复用性，使用List
def fab(max):
    n , a, b = 0, 0, 1
    L = []
    while n<max:
        L.append(b)
        print(L)
        a ,b = b ,a+b
        n = n+1
    return L

for n in fab(6):
    print (n)


#使用生成器，yield 类似于断点
def fab(max):
    n , a, b = 0, 0, 1
    while True:
        if (n>max):
            return 
        yield a #暂停函数并返回a的值
        yield b #暂停函数并返回b的值
        a ,b = b ,a+b
        #print('a = %d,b = %d'%(a,b))
        n = n+1
        
f = fab(8)

while True:
    try:
        print (next(f),end=" ")#next继续调用函数
    except:
        break

格式

#str.formate
print('{}网址："{}"!'.format('百度','www.baidu.com'))
print('{1} and {0}'.format('Tom','Jerry'))
print('{mao} and {shu}'.format(mao = 'Tom', shu = 'Jerry'))

import math
print('PI的值近似为{0:.3f}。'.format(math.pi))