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I have a general question about the "do...until" iteration until a condition is met.

Let's say that I have a variable x, y and z, where:

x0 = function(y0) I ran the code, and from the function, I got a value x0 from an inputted variable value y0. With the value of x0, now I have to update y0 and get a new value of y1=function(x0). The process is repeated in the next step, and now I should get: x1 = function(y1) and again, from x1, to update y1 and get a new value of y2=function(x1).

The iteration should stop when the condition of x(i-1) - x(i) =~ 0 is met, and after that, it should continue with a new calculation, which will have:

z = function(y(i))

I'm new to these "do...until" iterations, and my main problem is setting up the condition.

Here is a picture of the results of the example that I solved by running the code a few times manually iterating:

Manual Iteration

I didn't post the code for the functions because they are long. I really appreciate any help you can provide.

toyota Supra
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bennu777
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    *"I didn't post the code..."* It's really helpful to see your code. Maybe you can boil it down to a simple example so it isn't so long? – C.Nivs Sep 01 '22 at 14:53
  • [This](https://realpython.com/python-while-loop/) explain the usage of `while True` and break condition. Can be useful. – Glauco Sep 01 '22 at 15:09

1 Answers1

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This works just like the "do ... until" you described:

while not [condition]:
    ...

so you can write either something like this:

y = y0
x = function(y)
last_x = -1

while not (-.0001 <= last_x - x <= .0001):
    y = function(x)
    last_x = x
    x = function(y)
    print(x, y, last_x)

or (if you want to keep track of all your x's and y's):

y = [y0]
x = []

while len(x) <= 1 or not (-.0001 <= x[-2] - x[-1] <= .0001):
    x.append(function(y[-1]))
    y.append(function(x[-1]))
ACA
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