Question

我有b_x作为一个数组，我正在操作它，如代码所示。

G = 5
b_x =numpy.array([[0] for i in range(G)])
print(b_x)

for x in range(5):
    for y in range(5):
        b_x[x] += y*0.25
        print("y*0.25:" + " " + str(y*0.25))
        print("b_x[x]:" + " " + str(b_x[x][0]))
    print("end")
print(b_x)

添加后，我的b_x应该是：

[[2.5]
 [2.5]
 [2.5]
 [2.5]
 [2.5]]

但输出是不同的。所以，我添加了一些打印语句来检查，并得到以下输出：

[[0]
 [0]
 [0]
 [0]
 [0]]
y*0.25: 0.0
b_x[x]: 0
y*0.25: 0.25
b_x[x]: 0
y*0.25: 0.5
b_x[x]: 0  
y*0.25: 0.75
b_x[x]: 0
y*0.25: 1.0
b_x[x]: 1
end
y*0.25: 0.0
b_x[x]: 0
y*0.25: 0.25
b_x[x]: 0
y*0.25: 0.5
b_x[x]: 0
y*0.25: 0.75
b_x[x]: 0
y*0.25: 1.0
b_x[x]: 1 
end
y*0.25: 0.0
b_x[x]: 0
y*0.25: 0.25
b_x[x]: 0
y*0.25: 0.5
b_x[x]: 0
y*0.25: 0.75
b_x[x]: 0
y*0.25: 1.0
b_x[x]: 1
end
y*0.25: 0.0
b_x[x]: 0 
y*0.25: 0.25
b_x[x]: 0
y*0.25: 0.5
b_x[x]: 0
y*0.25: 0.75
b_x[x]: 0
y*0.25: 1.0
b_x[x]: 1
end
y*0.25: 0.0
b_x[x]: 0
y*0.25: 0.25
b_x[x]: 0
y*0.25: 0.5
b_x[x]: 0
y*0.25: 0.75
b_x[x]: 0
y*0.25: 1.0
b_x[x]: 1  
end
[[1] 
 [1]
 [1]
 [1]
 [1]]

最后，每个值都是1，这是错误的。在检查内部打印语句时，似乎在（y * 0.25）值为小数时不会添加元素。我已经检查了另一个代码，如果要添加的值是12.5，只有12个被添加到数组元素。为什么这会发生在numpy数组？

列表不会出现问题（如果我将b_x定义为列表），则会添加小数值。

Answer 1

更改

b_x =numpy.array([[0] for i in range(G)])

到

b_x =numpy.array([[0.0] for i in range(G)])

或更好

b_x =numpy.zeros((5,))

问题在于，您的版本b存储为整数，因此b[x] += (some smallish fraction)向下舍入为0.

除了“numpy”数组

1 个答案: