如何在递归循环中继续附加到 numpy 数组，然后打印出最终结果/将其传递给另一个 function？

Question

In recursion, how to use a numpy array to keep appending your values in it, and once the recursion is done, to return/pass it to the main function or outside the current function to print it out or use it for another function?

I've tried a lot of ways but none work, it would be great if someone could help me. I usually end up with a blank list for every recursion or the numpy array just gets written over and when i return it to the other function, it shows 0. This is a basic python question,, pls help. It would help if you could write the basic syntax with an example of updating an array within a recursion and printing out JUST the final updated array.

Answer 1

I do not know for sure what is causing a problem, but a common mistake is that you initialize the variable within the function call which makes a new local variable for every function call (even in recursion) and it does not know about the state of that variable in the "parent function" that called it.

You can do one of two things:

1. Create a global numpy array instead of a local one made on the stack for a specific call to a function.
2. Pass the numpy array to as an input to consequent function calls in the recursion loop

It depends on your use case or preference. The first one is pretty obvious. As for the second one, you could do something like:

function(arg1, arg2, ..., np_array=None, depth=0):

  if depth == 0:
    np_array = # Initialization of the array
  
  # Function stuff ...
  
  # For the recursive call
  depth += 1
  function(arg1, arg2, ..., np_array=np_array, depth=depth)
  
  if depth == 0: # Or at whatever depth you want to print the array  
  print(np_array) # After recursion ends

As a piece of advice: you can always avoid recursion by using some sort of data structure (like a stack) and a loop.