Basic BrainFuck interpreter
This being Python, it should be relatively easy to present the illusion of an infinite tape, at least in the positive direction.  I don't see reason that cell_amount has to be specified, and the user shouldn't have to worry about such details.

Your input and output routines are wrong:


The . instruction should print one character, interpreting the cell value as an ASCII code.  Instead, you print the cell value as a base-10 number, followed by Newline.
The , instruction should read one character, storing its ASCII code as the cell value.  Instead, you read a string, and try to parse it as an integer.


while True: … is a lie.  What you really mean is while step &lt; steps: ….  Then you can get rid of the if step == steps: exit(0) at the end of the loop.