CODEWITHSUNDEEP
pythonarrays
Victor J Mytre
Victor J Mytre

Reputation: 354

Creating a 2d array based on two different arrays

I receive constant data, for ease of life I get both data values that I receive and put them into each into a different array, the idea of this is so that I can link a value of Variable2 to a value of Variable1. Now, Variable1 will always be a value between 0 and 7, which I want to use this value to index the other array containing all values from variable2, data is polled serially inside a for loop, so I get data for both variables constantly. an example of data I get:

Variable1:  6 Variable2:  1499.6
Variable1:  6 Variable2:  1186.5
Variable1:  6 Variable2:  570.4
Variable1:  1 Variable2:  405.9
Variable1:  1 Variable2:  754.0
Variable1:  1 Variable2:  197.2
Variable1:  1 Variable2:  726.0
Variable1:  1 Variable2:  959.1
Variable1:  1 Variable2:  709.6

An example of two arrays of data for variable1 and variable 2 is below:

  Variable2 ={  [1499.6, 1186.5, 570.4, 405.9, 754.0, 197.2, 726.0, 959.1, 709.6]}
  Variable1 ={  [[6], [6], [6], [1], [1], [1], [1], [1], [1]]}

So my question is how would I grab these two arrays and make it so for example if I where to do print(VariableArray[6][2]) results in it printing : 570.4 which is the 3rd variable2 corresponding to Variable1 = 6

Upvotes: 3

Views: 68

Answers (1)

Paul
Paul

Reputation: 21975

I'd go with a dictionary of lists:

{
    6: [1499.6, 1186.5, 570.4],
    1: [405.9, 754.0, 197.2, 726.0, 959.1, 709.6]
}

As an example in the Python REPL:

>>> d = {6: [1499.6, 1186.5, 570.4], 1: [405.9, 754.0, 197.2, 726.0, 959.1, 709.6]}
>>> d[6][2]
570.4

The idea is: Keep a key for your 0 to 7 values (initially Variable1) and for each of those, store a list of values where you push the new data.

You could initialize this dictionary like so:

d = {
    0: [],
    1: [],
    2: [],
    3: [],
    4: [],
    5: [],
    6: [],
    7: [],
}

Or you could use a defaultdict, but first, make sure you understand lists and dictionaries.

In order to append data to a list you'd do (assuming 42.0 is your new value and the dictionary already contains the data you posted in the question):

d[6].append(42.0)

Which yields:

{6: [1499.6, 1186.5, 570.4, 42.0], 1: [405.9, 754.0, 197.2, 726.0, 959.1, 709.6]}

Or more generally: d[Variable1].append(Variable2).

Note: make sure your list will not grow indefinitely.

Please read the general theory and usage on dictionaries and lists in Python here (minimal reading for better understanding):

Upvotes: 4

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