问题描述
具有这样的numpy数组:
Having numpy array like that:
a = np.array([35,2,160,56,120,80,1,1,0,0,1])
我想从数组的第一个元素中减去自定义值(例如5).基本上可以做到:a[0] - 5
I want to subtract custom value (for example, 5) from first element of the array. Basically it can be done like:a[0] - 5
但是如何将结果应用于初始数组，并用答案替换第一个值?
But how can I apply this result to the initial array and replace the first value with the answer?
谢谢！
推荐答案
您可以使用:
a[0] -= 5 # use -=这会将a变成:
>>> a = np.array([35,2,160,56,120,80,1,1,0,0,1])
>>> a[0] -= 5
>>> a
array([ 30, 2, 160, 56, 120, 80, 1, 1, 0, 0, 1])
对于大多数操作(+，-，*，/等)，有一个就地"等效项(+=，-=，*=，/=等等)，该操作将与正确的操作数一起应用，然后将其存储回去.
For most operations (+, -, *, /, etc.), there is an "inplace" equivalent (+=, -=, *=, /=, etc.) that will apply that operation with the right operand and store it back.
请注意，如果要减去 all 个元素，则不应该使用Python for循环，这样做有更有效的方法.
Note that if you want to subtract all elements, you should not use a Python for loop, there are more efficient ways for that.
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