CODEWITHSUNDEEP
pythonargs
Abdullah Bera Koksal
Abdullah Bera Koksal

Reputation: 49

Finding a specific index in a list

I'm trying to do a project where I need to track a robots final position [0, 0] after giving it limitless coordinates. The coordinates can also be in negative. For example north equals -10 is the same as south equals 10. So the coordinates are in the order of north, east, south, and west. Example arguments: track_robot(1, 2, 3, 4, 5, 6, 7, 8, 9, 10), track_robot(20, 30, 10, 40), track_robot(10, -10, -10, 10)

This is my code:

# give as much coordinates as you want to the bot and return it's final position.
# north, east, south, west

def track_robot(*steps):
    pos = []
    north = 0
    east = 0
    south = 0
    west = 0
    for coord in steps:
        if steps.index(coord) % 2 == 0:
            if steps.index(coord) % 4 == 0:
                if coord < 0:
                    south += coord
                else:
                    north += coord
            else:
                if coord < 0:
                    north += abs(coord)
                else:
                    south -= coord
        else:

I managed to handle the y axis so north and south using their index values in the *steps variable, but couldn't seem to come up with an idea how to do it for the x axis(east and west). I got stuck at the end of my code. Can you please help me?

Upvotes: 0

Views: 326

Answers (1)

RobertoT
RobertoT

Reputation: 1683

Instead of using a for looping and indexing, you can work with a list as a input and extract the 4 coordinates as 4 different arrays. The trick is the reshape function for numpy library.

import numpy as np

def track_robot(*steps):
    """
    Input: 'steps' is a list of numbers: coordinates N,E,S,W
    
    Returns 4 different arrays for N, E, S and W
    """
    # Convert list to array (numpy array)
    arr = np.asarray(steps)
    # Check array has same steps for the same coords (N,E,S,W)
    if len(arr) % 4 != 0:
        # Calculate how much coords left:
            # If length % 4 != 0, then length/4 has a decimal part.
            # If we get the integer part of the fraction we can know the 
            # next subgroup of coordinates we need. We multiply by 4 
            # and subtract the length so we calculated how many coord
            # we don't have (E, S and/or W).
        nzeros = 4*(int(len(arr)/4)+1)-len(arr)
        # Add the number of zeros (no-movement in previous coords)
        arr = np.pad(arr, (0, nzeros), 'constant')
    # Now, we reshape as a matrix 4xM, where M columns = len(arr)/4
    # and 4 rows, each one for each coordinate.
    arr = arr.reshape([int(len(arr)/4),4], order = 'F')
    # Now split columns
    
    north = arr[0]
    east = arr[1]
    south = arr[2]
    west = arr[3]
    return north,east,south,west

First, you have to convert the list to a numpy array. I assumed coordinates are always sorted the same: North, East, South, West, so we can reshape the array as a matrix of 4 rows and extract each row individually. But for using reshape function, the length of the array has to be % 4 == 0. Therefore, if it isn't, we have to fill it with zeros using the pad function. (zero = no-movement for that coordinate).

Try with:

   # 1 = North, 2 = East, 3 = South, 4 = West. Last steps for 
    # south and west are missing.
    track_robot(1,2,3,4,1,2,3,4,1,2,3,4,1,2)

If it was helpful consider to vote as the solution :)

Upvotes: 1

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