将第一个数组的每个元素与第二个数组的所有元素相加

Question

I have two arrays:

array1 = [1,2,3]
array2 = [10,20,30]

I want the next sum:

array3 = [10+1,10+2,10+3,20+1,20+2,20+3,30+1,30+2,30+3]

How can I do that? (I know that it can be done with two for loops but I want something more efficient if possible)

Note: those two arrays are contained in a dataframe (pandas)

Answer 1

I do not think pandas is necessary here

[x+y for x in array2 for y in array1]
Out[293]: [11, 12, 13, 21, 22, 23, 31, 32, 33]

If they are in the dataframe

df=pd.DataFrame({'a':array1,'b':array2})
df
Out[296]: 
   a   b
0  1  10
1  2  20
2  3  30
df.a.values+df.b.values[:,None]
Out[297]: 
array([[11, 12, 13],
       [21, 22, 23],
       [31, 32, 33]], dtype=int64)

Update

(df.a.values+df.b.values[:,None]).ravel()
Out[308]: array([11, 12, 13, 21, 22, 23, 31, 32, 33], dtype=int64)

Answer 2

I wanted to recommend using itertools.product here, https://docs.python.org/3/library/itertools.html included a lot of other recipes that allows you to code more clearly

from itertools import product

array1 = [1,2,3]
array2 = [10,20,30]
[x+y for x,y in product(array1,array2)]

# fp style
[*map(sum, product(array1,array2))]