阿萨姆奶茶一箱15支装。
在http://www.ds365.com/ 的价格是44
在http://www.synergyiclub.com:8086/ 的价格是45
外面零售是4.5一支
在计算对比是，44/15 的结果变成了2，实际应该是2.9333333
WHY？
代码：
-----------------------------------
box_ds = 44
box_syn = 45
num_in_box = 15
per_sale_retail_price = 4
print "Here is the incorrect method:"
per_ds_incorrect = box_ds / num_in_box #Why did it calculate incorrectly here?
print "See what will happen now:"
per_ds = float(box_ds) / float(num_in_box)
per_syn = box_syn / num_in_box
print per_ds
print per_ds_incorrect
print "The num what I want is %f" % per_ds
print "The num what I don't want is %r " % per_ds_incorrect
print "The price of a bottle Asamu Milktea on ds is : %r" % per_ds
print "The price of a bottle Asamu Milktea on Synergy is : %s" % per_syn
print "The price of a bottle Asamu Milktea on retail is : %r" % per_sale_retail_price
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总结：必须使用浮点型，但是以下是错的：
float(per_ds_incorrect = box_ds / num_in_box)
float(per_ds_incorrect）= box_ds / num_in_box
per_ds_incorrect）= float(box_ds / num_in_box
正确的是：
per_ds = float(box_ds) / float(num_in_box)
