Python单行“for”表达式

Question

I'm not sure if I need a lambda, or something else. But still, I need the following:

I have an array = [1,2,3,4,5] . I need to put this array, for instance, into another array. But write it all in one line.

for item in array:
    array2.append(item)

I know that this is completely possible to iterate through the items and make it one-line. But googling and reading manuals didn't help me that much... if you can just give me a hint or name this thing so that I could find what that is, I would really appreciate it.

Update: let's say this: array2 = SOME FANCY EXPRESSION THAT IS GOING TO GET ALL THE DATA FROM THE FIRST ONE

(the example is NOT real. I'm just trying to iterate through different chunks of data, but that's the best I could come up with)

Answer 1

The keyword you're looking for is list comprehensions :

>>> x = [1, 2, 3, 4, 5]
>>> y = [2*a for a in x if a % 2 == 1]
>>> print(y)
[2, 6, 10]

Answer 2

for item in array: array2.append (item)

或者，在这种情况下：

array2 += array

Answer 3

如果您要复制数组：

array2 = array[:]

Answer 4

If you really only need to add the items in one array to another, the '+' operator is already overloaded to do that, incidentally:

a1 = [1,2,3,4,5]
a2 = [6,7,8,9]
a1 + a2
--> [1, 2, 3, 4, 5, 6, 7, 8, 9]

Answer 5

甚至array2.extend(array1)都可以工作。

Answer 6

Using elements from the list 'A' create a new list 'B' with elements, which are less than 10

Option 1:

A = [1, 1, 2, 3, 5, 8, 13, 4, 21, 34, 9, 55, 89]

B = []
for i in range(len(A)):
    if A[i] < 10:
        B.append(A[i])
print(B)

Option 2:

A = [1, 1, 2, 3, 5, 8, 13, 4, 21, 34, 9, 55, 89]

B = [A[i] for i in range(len(A)) if A[i] < 10]
print(B)

Result: [1, 1, 2, 3, 5, 8, 4, 9]