在python清单上附加始终相同的值 [英] List on python appending always the same value
问题描述
我在while循环中有以下代码.
I have the following code inside a while loop.
if gender == 0 and len(men) < 51 :
height = float((random.uniform(1.3, 1.9) + (random.randint(10, 20)/100.)).__format__('.2f'))
weight = float((random.uniform(45, 100) * height).__format__('.2f'))
attr['height'] = height
attr['weight'] = weight
men.append(attr)
因此，此代码始终提供一些随机的高度和随机的权重.但是异地循环(完成时).如果我执行print men，则会得到以下结果:
So this code always gives some random height and random weight. But outsite de loop (when it is finished). If I do print men, I get the following result:
[{'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}, {'weight': 76.64, 'height': 1.75}]
总是一样.但是，如果我不使用attr[height] = height; attr['weight] = weight而是使用men.append(height); men.append(weight)，则会得到以下结果:
Its always the same thing. But, if I instead of using attr[height] = height; attr['weight] = weight and use men.append(height); men.append(weight) I get the following result:
print men
[1.91, 145.95, 1.64, 95.66, 2.0, 159.94, 1.74, 143.36, 1.68, 97.99, 1.6, 90.11, 1.63, 116.2, 1.56, 96.8, 2.04, 198.56, 1.56, 145.96, 1.44, 67.57, 1.83, 94.97, 1.85, 175.69, 1.84, 101.84, 1.54, 135.0, 1.41, 101.23, 1.92, 167.59, 1.74, 142.55, 1.49, 129.07, 1.83, 161.28, 1.59, 97.16, 1.46, 134.53, 2.03, 158.72, 2.05, 184.43, 1.97, 162.81]
print men
[1.91, 145.95, 1.64, 95.66, 2.0, 159.94, 1.74, 143.36, 1.68, 97.99, 1.6, 90.11, 1.63, 116.2, 1.56, 96.8, 2.04, 198.56, 1.56, 145.96, 1.44, 67.57, 1.83, 94.97, 1.85, 175.69, 1.84, 101.84, 1.54, 135.0, 1.41, 101.23, 1.92, 167.59, 1.74, 142.55, 1.49, 129.07, 1.83, 161.28, 1.59, 97.16, 1.46, 134.53, 2.03, 158.72, 2.05, 184.43, 1.97, 162.81]
如果我在循环内打印attr，它总是具有不同的值(它是我想要的).但是，当我将其追加到列表中时，列表的值始终相同.我在做什么错了?
If I print attr inside the loop it always has a different value ( its what I want). But when I append it to my list, the values of my list are always the same. What am I doing wrong?
推荐答案
当前简化的代码示例，用于更全面地解释为什么您的结果是:
A simplified example of your code currently to explain more fully why your results are the way they are:
all_items = []
new_item = {}
for i in range(0,5):
new_item['a'] = i
new_item['b'] = i
all_items.append(new_item)
print new_item
print hex(id(new_item)) # print memory address of new_item
print all_items
请注意，每次循环时，对象的内存地址与每次 相同.这意味着每次添加的对象都是相同的.因此，当您打印最终列表时，您将在循环中的每个位置打印相同对象的坐标.
Notice the memory address for your object is the same each time you go through your loop. This means that your object being added is the same, each time. So when you print the final list, you are printing the coordinates of the same object at every location in the loop.
每次循环时，值都会被更新-假设您每天都在同一堵墙上绘画.第一天，可能是蓝色的.第二天，您重新粉刷相同的墙(或对象)，然后变为绿色.最后一天，您将其绘制成橙色，然后变为橙色-现在同一面墙总是 橙色.您对attr对象的引用就像说您有同一堵墙.
Each time you go through the loop, the values are being updated - imagine you are painting over the same wall every day. The first day, it might be blue. The next day, you repaint the same wall (or object) and then it's green. The last day you paint it orange and it's orange - the same wall is always orange now. Your references to the attr object are like saying you have the same wall.
即使您在涂完油漆后看着墙壁，颜色也会改变.但是之后是橙色的墙-即使您看了5次也是如此.
Even though you looked at the wall after painting it, the color changed. But afterwards it is a orange wall - even if you look at it 5 times.
在每次迭代中将对象设为新对象时，请注意发生了两件事:
When we make the object as a new object in each iteration, notice two things happen:
- 内存地址更改
- 这些值作为唯一值持久存在
这类似于绘制不同墙.在完成最后一幅墙的绘制之后，先前的每堵墙仍会以您首先绘制的颜色进行绘制.
This is similar to painting different walls. After you finish painting the last one, each of the previous walls is still painted the color you first painted it.
您可以在下面看到的每个迭代创建每个对象的地方:
You can see this in the following, where each object is created each iteration:
all_items = []
for i in range(0,5):
new_item = {}
new_item['a'] = i
new_item['b'] = i
all_items.append(new_item)
print hex(id(new_item))
print all_items
您还可以采用其他方式，例如:
You can also do in a different way, such as:
all_items = []
for i in range(0,5):
new_item = {'a': i, 'b': i}
all_items.append(new_item)
print hex(id(new_item))
print all_items
甚至一步一步来完成
all_items = []
for i in range(0,5):
all_items.append({'a': i, 'b': i})
print all_items
因此，以下任何一种都可以工作:
Either of the following will therefore work:
attr = {}
attr['height'] = height
attr['weight'] = weight
men.append(attr)
或:
men.append({'height': height, 'weight': weight})
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