Learn Encapsulation by Building a Projectile Trajectory Calculator - Step 20

Python
1

Tell us what’s happening:

I can’t figure out how to join the inner lists and return anything that looks like the example. This is the closest thing I found in my searching to joining them. What I get though is a bunch of " . " running down the left side. A little guidance would be appreciated. Thanks

Your code so far

import math
import itertools
from functools import reduce

GRAVITATIONAL_ACCELERATION = 9.81
PROJECTILE = "∙"
x_axis_tick = "T"
y_axis_tick = "⊣"

class Projectile:
    __slots__ = ('__speed', '__height', '__angle')

    def __init__(self, speed, height, angle):
        self.__speed = speed
        self.__height = height
        self.__angle = math.radians(angle)
        
    def __str__(self):
        return f'''
Projectile details:
speed: {self.speed} m/s
height: {self.height} m
angle: {self.angle}°
displacement: {round(self.__calculate_displacement(), 1)} m
'''

    def __calculate_displacement(self):
        horizontal_component = self.__speed * math.cos(self.__angle)
        vertical_component = self.__speed * math.sin(self.__angle)
        squared_component = vertical_component**2
        gh_component = 2 * GRAVITATIONAL_ACCELERATION * self.__height
        sqrt_component = math.sqrt(squared_component + gh_component)
        
        return horizontal_component * (vertical_component + sqrt_component) / GRAVITATIONAL_ACCELERATION
        
    def __calculate_y_coordinate(self, x):
        height_component = self.__height
        angle_component = math.tan(self.__angle) * x
        acceleration_component = GRAVITATIONAL_ACCELERATION * x ** 2 / (
                2 * self.__speed ** 2 * math.cos(self.__angle) ** 2)
        y_coordinate = height_component + angle_component - acceleration_component

        return y_coordinate
    
    def calculate_all_coordinates(self):
        return [
            (x, self.__calculate_y_coordinate(x))
            for x in range(math.ceil(self.__calculate_displacement()))
        ]

    @property
    def height(self):
        return self.__height

    @property
    def angle(self):
        return round(math.degrees(self.__angle))

    @property
    def speed(self):
        return self.__speed

    @height.setter
    def height(self, n):
        self.__height = n

    @angle.setter
    def angle(self, n):
        self.__angle = math.radians(n)

    @speed.setter
    def speed(self, s):
       self.__speed = s
    
    def __repr__(self):
        return f'{self.__class__}({self.speed}, {self.height}, {self.angle})'

class Graph:
    __slots__ = ('__coordinates')

    def __init__(self, coord):
        self.__coordinates = coord

    def __repr__(self):
        return f"Graph({self.__coordinates})"

    def create_coordinates_table(self):
        table = '\n  x      y\n'
        for x, y in self.__coordinates:
            table += f'{x:>3}{y:>7.2f}\n'

        return table


# User Editable Region

    def create_trajectory(self):
        
        rounded_coords = [(round(x), round(y)) for x,y in self.__coordinates]
        
        x_max = max(rounded_coords, key=lambda i: i[0])[0]
        y_max = max(rounded_coords, key=lambda j: j[1])[1]
        
        matrix_list = [[' ' for _ in range(x_max + 1)] for _ in range(y_max + 1)]
        
        for (x, y) in rounded_coords:
            matrix_list[-y-1][x] = PROJECTILE
        result = [item for sublist in matrix_list for item in sublist]

        
        return result


# User Editable Region


ball = Projectile(10, 3, 45)
print(ball)
coordinates = ball.calculate_all_coordinates()
graph = Graph(coordinates)
for row in graph.create_trajectory():
    print(row)

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Challenge Information:

Learn Encapsulation by Building a Projectile Trajectory Calculator - Step 20

2

Join the inner lists to have a list of strings.

You’re on the right track, but you will need to use join() to join the inner lists

And you need to review how to do a list comprehension, you have too many for/ins but this is definitely in the right direction.

3

Yeah, that was actually some code I found doing a google search trying to figure out how to join the inner lists.

4

You just need to use a basic list comprehension to go through matrix_list (basic meaning no if statment) and a join().

Join all the elements so they form a string, instead of separate elements of a list.

https://www.w3schools.com/python/python_lists_comprehension.asp

newlist = [x for x in fruits]

https://www.w3schools.com/python/ref_string_join.asp

To make a string out of a list using join() is like this:

string = "".join(list)

You just need to combine these into 1 line of code.

I hope this helps!

5

That does help. Thank you very much. The funny thing is I woke up in the middle of the night and the solution came to me and it is exactly how you explained it. I was over thinking this one. Thanks for unsticking me.

Tom

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