举例详解Python中循环语句的嵌套使用

Python编程语言允许在一个循环内嵌套另一个循环。下面将介绍几个例子来说明这一概念。
语法

在Python中嵌套循环语句的语法如下：

    for iterating_var in sequence:
      for iterating_var in sequence:
       statements(s)
      statements(s)

Python编程语言允许在一个循环内嵌套另一个循环。下面将介绍几个例子来说明这一概念。
语法

在Python中嵌套循环语句的语法如下：

    for iterating_var in sequence:
      for iterating_var in sequence:
       statements(s)
      statements(s)

Python编程语言的一个嵌套while循环语句的语法，如下所示：

    while expression:
      while expression:
       statement(s)
      statement(s)

在循环嵌套最后需要说明的是，可以把任何类型的循环的任何其他类型的循环里面。例如，for循环内可以放置while循环，反之亦然。
例子

下面的程序使用一个嵌套的循环，从2到100中找出所有的素数：

    #!/usr/bin/python

    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 prime"
      i = i + 1

    print "Good bye!"

当执行上面的代码，它会产生以下结果：

    2 is prime
    3 is prime
    5 is prime
    7 is prime
    11 is prime
    13 is prime
    17 is prime
    19 is prime
    23 is prime
    29 is prime
    31 is prime
    37 is prime
    41 is prime
    43 is prime
    47 is prime
    53 is prime
    59 is prime
    61 is prime
    67 is prime
    71 is prime
    73 is prime
    79 is prime
    83 is prime
    89 is prime
    97 is prime
    Good bye!