Advent Of Code Day 3 Part 1 v2

import matplotlib.pyplot as plt


def trace(l, direction, steps):
    if steps == 0:
        return l
    else:
        if direction == 'U':
            while steps > 0:
                new_coord = (l[-1][0], l[-1][1] + 1)
                l.append(new_coord)
                steps -= 1
            return l
        elif direction == 'D':
            while steps > 0:
                new_coord = (l[-1][0], l[-1][1] - 1)
                l.append(new_coord)
                steps -= 1
            return l
        elif direction == 'R':
            while steps > 0:
                new_coord = (l[-1][0] + 1, l[-1][1])
                l.append(new_coord)
                steps -= 1
            return l
        elif direction == 'L':
            while steps > 0:
                new_coord = (l[-1][0] - 1, l[-1][1])
                l.append(new_coord)
                steps -= 1
            return l


f = open('input.txt', 'r')
instructions1, instructions2 = f.readlines()
f.close()
instructions1 = instructions1.split(',')
instructions2 = instructions2.split(',')

# test case 1
# instructions1 = ['R75', 'D30', 'R83', 'U83', 'L12', 'D49', 'R71', 'U7', 'L72']
# instructions2 = ['U62', 'R66', 'U55', 'R34', 'D71', 'R55', 'D58', 'R83']

# test case 2
# instructions1 = ['R98', 'U47', 'R26', 'D63', 'R33', 'U87', 'L62', 'D20', 'R33', 'U53', 'R51']
# instructions2 = ['U98', 'R91', 'D20', 'R16', 'D67', 'R40', 'U7', 'R15', 'U6', 'R7']

coords1 = [(0, 0)]
for instruction in instructions1:
    coords1 = trace(coords1, instruction[0], int(instruction[1:]))
coords2 = [(0, 0)]
for instruction in instructions2:
    coords2 = trace(coords2, instruction[0], int(instruction[1:]))

crossings = set(coords1) & set(coords2)

print(crossings)
for x in crossings:
    print(x[0] + x[1])

plt.scatter(*zip(*crossings))
plt.plot(*zip(*coords1), 'r-')
plt.plot(*zip(*coords2), 'b-')
plt.show()