Problem with for loop and creating list of list

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I have an numpy array called expected which is a list of a list of a list. 

expected =  [[[45.0, 10.0, 10.0], [110.0, 10.0, 8.0], [60.0, 10.0, 5.0], [170.0, 10.0, 4.0]], [[-80.0, 20.0, 10.0], [97.0, 15.0, 12.0], [5.0, 20.0, 8.0], [93.0, 10.0, 8.0], [12.0, 5.0, 15.0], [-88.0, 10.0, 10.0], [176.0, 10.0, 8.0]]]

I want to put it through a loop without having to hardcode so its applicable to different lengths of list.

When the loop runs for the first time i want it to solve this:

horizontal_exp = expected[0][0][1]*expected[0][0][2]
*np.cos(np.deg2rad(expected[0][0][0]))

Then the next loop to be like this:

horizontal_exp = expected[1][1][1]*expected[1][1][2]
*np.cos(np.deg2rad(expected[1][1][0]))

And the following loop to be like this:

horizontal_exp = expected[2][2][1]*expected[2][2][2]
*np.cos(np.deg2rad(expected[2][2][0]))

and so on until it finished the different sections of rows.

I don't understand why the 'i' never worked??

In the end I want horizontal expected to be a list of a list

e.g.

expected = [ [12,21,23,34], [12,32,54,65,76,87,65] ] # These are not the values I'm just giving an example

where the [12,21,23,24] corresponds to the [[45.0, 10.0, 10.0], [110.0, 10.0, 8.0], [60.0, 10.0, 5.0], [170.0, 10.0, 4.0]]

and the [12,32,54,65,76,87,65] corresponds to the [[-80.0, 20.0, 10.0], [97.0, 15.0, 12.0], [5.0, 20.0, 8.0], [93.0, 10.0, 8.0], [12.0, 5.0, 15.0], [-88.0, 10.0, 10.0], [176.0, 10.0, 8.0]]

I'm unsure how to do this, I know you have to append it with a for loop but how do you separate it into a list of a list??

horizontal_expected = []
for i in list(range(len(expected[i]))):
    horizontal_exp = expected[i][i][1]*expected[i][i][2]
    *np.cos(np.deg2rad(expected[i][i][0]))

    horizontal_expected.append(horizontal_exp)
    print(horizontal_expected)
python
1 Answers

The reason why you don't see the desired output is that, even though you have nested list expected, you are iterating only through the nested lists. You first need to iterate through the outer lists and then iterate through the nested lists internally:

import numpy as np
expected = [ [[45.0, 10.0, 10.0], [110.0, 10.0, 8.0], [60.0, 10.0, 5.0], [170.0, 10.0, 4.0]], [[-80.0, 20.0, 10.0], [97.0, 15.0, 12.0], [5.0, 20.0, 8.0], [93.0, 10.0, 8.0], [12.0, 5.0, 15.0], [-88.0, 10.0, 10.0], [176.0, 10.0, 8.0]] ]
horizontal_expected = []
for i in range(len(expected)):
    tmp_list = []
    for j in range(len(expected[i])):
        horizontal_exp = expected[i][i][1]*expected[i][i][2]*np.cos(np.deg2rad(expected[i][i][0]))
        tmp_list.append(horizontal_exp)
    horizontal_expected.append(tmp_list)
print(horizontal_expected)

The output of that is a list of lists:

>>> print(horizontal_expected)
[[70.71067811865476, 70.71067811865476, 70.71067811865476, 70.71067811865476], [-21.936481812926527, -21.936481812926527, -21.936481812926527, -21.936481812926527, -21.936481812926527, -21.936481812926527, -21.936481812926527]]

As you can see, it holds a value for each of the lists in the input, but the value is the same. This is due to the way that your equation was set up.

You want the indices to be updated based on the level of the loop: horizontal_exp = expected[i][j][1]*expected[i][j][2]*np.cos(np.deg2rad(expected[i][j][0]))

The full working code would look like this:

import numpy as np
expected = [ [[45.0, 10.0, 10.0], [110.0, 10.0, 8.0], [60.0, 10.0, 5.0], [170.0, 10.0, 4.0]], [[-80.0, 20.0, 10.0], [97.0, 15.0, 12.0], [5.0, 20.0, 8.0], [93.0, 10.0, 8.0], [12.0, 5.0, 15.0], [-88.0, 10.0, 10.0], [176.0, 10.0, 8.0]] ]
horizontal_expected = []
for i in range(len(expected)):
    tmp_list = []
    for j in range(len(expected[i])):
        horizontal_exp = expected[i][j][1]*expected[i][j][2]*np.cos(np.deg2rad(expected[i][j][0]))
        tmp_list.append(horizontal_exp)
    horizontal_expected.append(tmp_list)
print(horizontal_expected)

And the output:

>>> print(horizontal_expected)
[[70.71067811865476, -27.361611466053496, 25.000000000000007, -39.39231012048832], [34.72963553338608, -21.936481812926527, 159.39115169467928, -4.186876499435507, 73.36107005503543, 3.489949670250108, -79.80512402078594]]
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