Robot Motion in Python

Question

I am trying to program a robot to move. The robot moves based on where currently is. There are four places where it can be:

LOCATION1 Motion Plan is like so,
5 6
3 4
1 2
Initial positon is (x1,y1)
This gets coded as (x1,y1)->(x1+dx,y1)->(x1,y1+dy)->(x1+dx,y1+dy) ... and so on

LOCATION2 Motion Plan is like so,
5 3 1
6 4 2
The initial position is (x1,y1)
This gets coded as (x1,y1)->(x1,y1-dy)->(x1-dx,y1)->(x1-dx,y1-dy) ... and so on

LOCATION3 Motion Plan is like so,
6 5
4 3
2 1
Initial positon is (x1,y1)
This gets coded as (x1,y1)->(x1-dx,y1)->(x1,y1+dy)->(x1-dx,y1+dy) ... and so on

LOCATION4 Motion Plan is like so,
6 4 2
5 3 1
The initial position is (x1,y1)
This gets coded as (x1,y1)->(x1,y1+dy)->(x1-dx,y1)->(x1-dx,y1+dy) ... and so on

I am struggling to come up with a good pythonic way to code this. I am thinking on the lines of defining 4 different next move rules and then having a bunch of if statements that choose the correct rules

Has someone done something similar... Is there a better way

Answer 1

I know that this could be made more elegant(and the names for my methods are awful!), but maybe something like this?

>>> import itertools
>>> def alternator(*values):
...     return itertools.cycle(values)
... 
>>> def increasor(value_1, dvalue_1, steps=2):
...     counter = itertools.count(value_1, dvalue_1)
...     while True:
...             repeater = itertools.repeat(counter.next(), steps)
...             for item in repeater:
...                 yield item
... 
>>> def motion_plan(x_plan, y_plan, steps=6):
...     while steps > 0:
...         yield (x_plan.next(), y_plan.next())
...         steps -= 1
... 
>>> for pos in motion_plan(alternator('x1', 'x1+dx'), increaser('y1', '+dy'): #Location 1 motion plan
...     print pos
... 
('x1', 'y1')
('x1+dx', 'y1')
('x1', 'y1+dy')
('x1+dx', 'y1+dy')
('x1', 'y1+dy+dy')
('x1+dx', 'y1+dy+dy')

I was unsure how much flexibility you needed with this, you could reduce the complexity even further if you want to remove some flexibility. Additionally you almost certainly wouldn't be using strings for this, I just thought that it was the easiest way to demonstrate the idea. If you use numbers, then something like this:

>>> count = 0
>>> for pos in motion_plan(increaser(0, -1), alternator(0, 1)): #location 4 motion plan
...     print "%d %r" % (count, pos)
...     count += 1
1 (0, 0)
2 (0, 1)
3 (-1, 0)
4 (-1, 1)
5 (-2, 0)
6 (-2, 1)

Should correspond pretty clearly to this:

LOCATION4 Motion Plan is like so,
6 4 2
5 3 1

I believe that the motion plans would be as follows:

Location1 = motion_plan(alternator(0, 1), increasor(0, 1))
Location2 = motion_plan(increasor(0, -1), alternator(0, -1))
Location3 = motion_plan(alternator(0, -1), increasor(0, 1))
Location4 = motion_plan(increasor(0, -1), alternator(0, 1))

Answer 2

most pythonic way is StateMachine

Answer 3

You could do that, what you would do is.

def motion_loc1(x1,y1,dx,dy):
     # your operation


def motion_loc2(x1,y1,dx,dy):
     # your operation

And then in the main program, depending upon x1, y1 call the various motion methods.