Question

I was trying to do some simple manipulation of lists and numpy arrays and got stuck in some easy thing:

a=np.arange(12)
a
array([ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11])
a=np.reshape(a,(3,4))
a
array([[ 0,  1,  2,  3],
   [ 4,  5,  6,  7],
   [ 8,  9, 10, 11]])

b=np.arange(12,24)
b
array([12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23])
b=np.reshape(3,4)
list1 = [(a,'a'),(b,'b')]
data = [(i, j) for i,j in list1]

When I tried to do:

data[0][0]=np.delete(data[0][0], np.s_[-1::],0)

I got the following error:

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment

But if I do:

cop=np.delete(data[0][0], np.s_[-1::],0)
cop
array([[0, 1, 2, 3],
   [4, 5, 6, 7]])

It works perfectly fine.

But I also can’t do:

data[0][0]=np.copy(cop)

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment

But if I check the types, both are actually arrays:

type(cop)
<type 'numpy.ndarray'>

type(data[0][0])
<type 'numpy.ndarray'>

I couldn’t find the mistake for quite a few hours.

Answer 1

Then I realized that data is actually a tuple.

So this is what solves the problem:

data = [[i, j] for i,j in list1]

And then I can replace elements like data[0][0]