#!/usr/bin/python

# 1. while循环

# while <test>:

#     <statement1>

# else:

#     <statement2>

# while True:

#     print('Type Ctrl-C to stop me!')

x = 'spam'

while x:                        # 啥都可以拿到这里来判断

    print(x, end= ' ')

    x = x[1:]

print()

a=0; b=10

while a < b:

    print(a, end=' ')

    a += 1

print()

# break、continue、pass和循环中的else

# break: 跳出最近所在的循环

# continue: 跳到最近所在循环的开头处

# pass: 什么也不做, 只是空的占位语句

# else: 只有在循环正常离开时才会执行, 也就是没有碰到break语句

# pass是当语法需要语句但是又没有任何语句可写的时候就可以用这个

def fun1():

    pass

def fun2():

    print('老子还是干了事的')

fun2()                          # 调用函数

while True:

    name = input('Enter name:')

    if name == 'stop' : break

    age = input('Enter age:')

    print('Hello', name, '=>', int(age) ** 2)

# else是break从来不被执行之后会跳转过去的语句

y = 17

x = y // 2

while x > 1:

    if y % x == 0:

        print(y, 'has factor', x)

        break

    x -= 1

else:

    print(y, 'is prime')

# Python中的语句就是语句而不是表达式

# 2. for循环

# for <target> in <object>:

#     <statements>

#     if <test>: break

#     if <test>: continue

# else:

#     <statements>

for x in ["spam", "eggs", "ham"]:

    print(x, end=' ')

print()

sum = 0

for x in [1, 2, 3, 4]:

    sum = sum + x

print('sum = ', sum)

# 任何序列都适用于for循环, 甚至是某些根本不是序列的对象, 比如文件和字典

T = [(1, 2), (3, 4), (5, 6)]

for (a, b) in T:

    print(a, b)

D = {'a':1, 'b':2, 'c':3}

for key in D:

    print(key, '=>', D[key])

print(list(D.items()))

# range可以产生范围

# zip并行遍历以及构造字典

# enumerate生成偏移量和元组构成的元组

S = 'spam'

E = enumerate(S)

print(next(E))