为多维数组的每个元素添加值

Question

I want to know how I can add a value to each element of a NXN multidimensional array. I tried [x+1 for x in multiArray], but this one yields only for a 1D array.

Maybe something like this:

multiArray = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

addingArray=[]
for i in range(3):
    for j in range(3):
        addingArray.append(multiArray[j]+1) #(adding 1 to each element here)  

But this seems to be wrong?

Answer 1

You're getting 1D array as result because you have addingArray as a simple list. So, you iterate over all the elements in your multiArray and add 1 to it and you're appending the result to a list.

---

For efficiency reasons, it is advisable to use NumPy for arrays. Then, you can simply use broadcasting to add value to each element of the array. Below is an illustration:

# input array
In [180]: multiArray = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) 

# add 1 to each value of the array
In [181]: multiArray + 1  
Out[181]: 
array([[ 2,  3,  4],
       [ 5,  6,  7],
       [ 8,  9, 10]])

If you indeed want a plain python list as the result for some reasons, you can simply cast it to one:

In [182]: (multiArray + 1).tolist()  
Out[182]: [[2, 3, 4], [5, 6, 7], [8, 9, 10]]

Answer 2

Indice-iteration

You need to have a inner list to get the inner results, and access the good value with multiArray[i][j] , also don't use constant 3 take the habit to use object length

addingArray=[]
for i in range(len(multiArray)):
    innerArray = []
    for j in range(len(multiArray[i])):
        innerArray.append(multiArray[i][j]+1)
    addingArray.append(innerArray)  

print(addingArray) # [[2, 3, 4], [5, 6, 7], [8, 9, 10]]

---

Value iteration

You can also iterate over the arra directly to simplify and don't both with indices

addingArray=[]
for inner in multiArray:
    innerArray = []
    for value in inner:
        innerArray.append(value+1)
    addingArray.append(innerArray)  

---

List comprehension

And shorten it with list comprehension syntax

multiArray = [[v+1 for v in inner] for inner in multiArray]
print(multiArray) # [[2, 3, 4], [5, 6, 7], [8, 9, 10]]