Ex32 for-loop

for 循环和 List 类型

循环语句在之前也涉及到，While循环。for循环，更适合做一些有确定循环数量的动作。while循环终止条件相对模糊。for常常于list类型联合使用。 list类型，类似于 C 语言中的数组概念，动态数组。list类型最大的好处，可以对内部元素进行读写操作，就像文件一样。这点十分给力，很多操作，都是动态调整的，实现难以确定具体内容，或元素类型或元素数量。碰到这种情况，list绝对是瑞士军刀一般的武器。

示例代码

Ex32 for循环示例代码，如下:

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the_count = [1,2,3,4,5]
fruits = ['apple', 'oranges', 'pears', 'apricots']
change = [1, 'pennies',2,'dimes',3,'quarters']
# this first kind of for-loop goes through a list
for number in the_count:
    print "This is count %d" % number
#same as above
for fruit in fruits:
    print "A fruit of type: %s" % fruit
# Also we can go through mixed lists too
# notice we have to use %r since we don't know what's in it
for i in change:
    print "I got %r" % i
# We can also build list, first strt with an empty one
elements = [ ]
# then use the range function to do 0 to 5 counts
for i in range(0,6):
    print "Adding %d to the list." % i
    # append is a function that lists understand
    elements.append(i)
# now we can print them out too
for i in elements:
    print "Element was : %d" % i

示例运行，结果如下图:

小结

for循环的循环变量(i，count…)不必单独定义，直接在语句中使用；
list数据类型，可以容纳多种类型数据混合，但是每个元素在都有自己的位置。另外，list类型，可以嵌套，实现多维数据。