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计算后总值不变(total value is not changing after calculation)

 我这里有一个jsfiddle。  
 在小提琴中有许多标记文本框。 在文本框中键入一个数字，然后单击添加问题按钮。 您将看到剩余的总分数等于10但不会改变。 剩余标记的数量应通过减去附加行中的每个数字来改变。  
 例如，如果剩余的总标记为10并且您追加四行，每行包含标记1 ，则剩余的总标记应为6 。 （ 10 - 4 = 6 ）但为什么不改变剩余的标记数量？  
 这是执行计算的函数：  
function calculateTotal()
{
   var totalweight = totalmarks;
   $("#qandatbl td.weight input").each(function (i, elm){
        totalweight = totalweight - Number($(elm).val(), 10);
    });

    $("#total-weight").text(totalweight);
}

I have a jsfiddle here. 
In the fiddle there is a number of mark textboxes. Type a number in the text box and keep clicking on the add question button. You will see that the total marks remaining equals 10 but it doesn't change. The number of marks remaining should change by subtracting each number in the appended row. 
For example, if total marks remaining is 10 and you append four rows, each row containing marks of 1, then total marks remaining should be 6. (10 - 4 = 6.) But why is it not changing the number of marks remaining? 
This is the function where it performs the calculation: 
function calculateTotal()
{
   var totalweight = totalmarks;
   $("#qandatbl td.weight input").each(function (i, elm){
        totalweight = totalweight - Number($(elm).val(), 10);
    });

    $("#total-weight").text(totalweight);
}

原文：https://stackoverflow.com/questions/14044149

更新时间：2024-03-26 11:03

最满意答案

 第一部分代码实际上是误导性的，并且依赖于lena是方形图像的事实：发生的事情等同于调用zip(range(xmax), range(ymax)) ，然后将每个结果元组设置为0 。 你可以看到这里可能出现的问题：如果xmax != ymax ，那么事情将无效：  
>>> test = lena[:,:-3]
>>> test.shape
(512, 509)
>>> xmax, ymax = test.shape
>>> test[range(xmax), range(ymax)] = 0
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: shape mismatch: objects cannot be broadcast to a single shape
 
 定义diag_max = min(xmax, ymax) ，然后设置lena[range(diag_max), range(diag_max)] = 0可能会更好。  
 第二个问题的答案更容易： range(from, to, step)是对range的一般调用：  
>>> range(1, 10, 2)
[1, 3, 5, 7, 9]
>>> range(1, 10, -2)
[]
>>> range(10, 1, -2)
[10, 8, 6, 4, 2]
>>> range(10, 0, -1)
[10, 9, 8, 7, 6, 5, 4, 3, 2, 1]
 
 特别是，这会反转先前的列表，因此从右到左而不是从左到右抓取对角线。 

The first bit of code is actually misleading, and relies on the fact that lena is a square image: what happens is equivalent to calling zip(range(xmax), range(ymax)), and then setting each of the resulting tuples to 0. You can see what could go wrong here: if xmax != ymax, then things won't work: 
>>> test = lena[:,:-3]
>>> test.shape
(512, 509)
>>> xmax, ymax = test.shape
>>> test[range(xmax), range(ymax)] = 0
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: shape mismatch: objects cannot be broadcast to a single shape
 
It would probably be better to define diag_max = min(xmax, ymax), and then set lena[range(diag_max), range(diag_max)] = 0.  
The answer to your second question is easier: range(from, to, step) is the general call to range: 
>>> range(1, 10, 2)
[1, 3, 5, 7, 9]
>>> range(1, 10, -2)
[]
>>> range(10, 1, -2)
[10, 8, 6, 4, 2]
>>> range(10, 0, -1)
[10, 9, 8, 7, 6, 5, 4, 3, 2, 1]
 
In particular, this reverses the previous list, and so grabs the diagonal from right to left instead of left to right.

计算后总值不变(total value is not changing after calculation)

最满意答案

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