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  • Python:循环语句

    while

    在某种条件下,执行某段程序

    >>> w=0
    >>> while w<5:
    ...     print 'w :',w
    ...     w=w+1
    ... 
    w : 0
    w : 1
    w : 2
    w : 3
    w : 4

    continue

    跳过位于之后的语句,开始下一轮循环

    #输出10以内偶数
    >>> c=1
    >>> while c<10:
    ...     c+=1
    ...     if c%2>0:
    ...             continue
    ...     print c
    ... 
    2
    4
    6
    8
    10

    break

    跳出循环

    >>> b=1
    >>> while 1:
    ...     print b
    ...     b+=1
    ...     if b>5:
    ...             break
    ... 
    1
    2
    3
    4
    5

    while..else

    >>> e=1
    >>> while e<5:
    ...     print e,'<5'
    ...     e+=1
    ... else:
    ...     print e,'=5'
    ... 
    1 <5
    2 <5
    3 <5
    4 <5
    5 =5

    for

    可以遍历整个序列

    >>> for f in 'hello':
    ...     print f
    ... 
    h
    e
    l
    l
    o

    索引

    >>> singer=['adele','taylor','lana']
    >>> for index in range(len(singer)):
    ...     print 'singer:',singer[index]
    ... 
    singer: adele
    singer: taylor
    singer: lana

    for..else

    >>> for num in range(10,20):
    ...     for i in range(2,num):
    ...             if num%i==0:
    ...                     j=num/i
    ...                     print '%d=%d*%d'%(num,i,j)
    ...                     break
    ...     else:
    ...             print num,'is a prime number'
    ... 
    10=2*5
    11 is a prime number
    12=2*6
    13 is a prime number
    14=2*7
    15=3*5
    16=2*8
    17 is a prime number
    18=2*9
    19 is a prime number

    嵌套

    #输出100以内所有素数

    #!/usr/bin/python
    # -*- coding: UTF-8 -*-
    i = 2
    while(i < 100):
       j = 2
       while(j <= (i/j)):
          if not(i%j): break
          j = j + 1
       if (j > i/j) : print i, "is a prime number"
       i = i + 1

      嵌套等价语句

    #!/usr/bin/python
    # -*- coding: UTF-8 -*-
    for num in range(2,101):
         for i in range(2,num):
                 if num%i==0:
                         j=num/i
                         break
         else:
                 print num,'is a prime number'
    #!/usr/bin/python
    # -*- coding: UTF-8 -*-
    import math
    for i in range(50, 100 + 1):
        for j in range(2, int(math.sqrt(i)) + 1):   #比 i的开平方小的最大整数
            if i % j == 0:
                break
        else:
            print i,'is a prime number'

    暂时这些,后续补充..

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  • 原文地址:https://www.cnblogs.com/lilip/p/5556341.html
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