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我正在學習如何使用書中的方法，並且在此練習中，我正在試圖找出彈丸的最大高度。我很確定我把等式寫入projectile.py，但每次執行Exercise 1.py時，我從cball.getMaxY()獲得的結果總是"-0.0 meters."我可能錯過了哪些簡單的事情？我在這種方法工作流程中缺少什麼？
# projectile.py
"""projectile.py
Provides a simple class for modeling the
flight of projectiles."""
from math import sin, cos, radians
class Projectile:
"""Simulates the flight of simple projectiles near the earth's
surface, ignoring wind resistance. Tracking is done in two
dimensions, height (y) and distance (x)."""
def __init__(self, angle, velocity, height):
"""Create a projectile with given launch angle, initial
velocity and height."""
self.xpos = 0.0
self.ypos = height
theta = radians(angle)
self.xvel = velocity * cos(theta)
self.yvel = velocity * sin(theta)
#Find time to reach projectile's maximum height
self.th = self.yvel/9.8
def update(self, time):
"""Update the state of this projectile to move it time seconds
farther into its flight"""
#Find max height
self.maxypos = self.yvel - (9.8 * self.th)
self.xpos = self.xpos + time * self.xvel
yvel1 = self.yvel - 9.8 * time
self.ypos = self.ypos + time * (self.yvel + yvel1)/2.0
self.yvel = yvel1
def getY(self):
"Returns the y position (height) of this projectile."
return self.ypos
def getX(self):
"Returns the x position (distance) of this projectile."
return self.xpos
def getMaxY(self):
"Returns the maximum height of the projectile."
return self.maxypos
# Exercise 1.py
from projectile import Projectile
def getInputs():
a = eval(input("Enter the launch angle (in degrees): "))
v = eval(input("Enter the initial velocity (in meters/sec): "))
h = eval(input("Enter the initial height (in meters): "))
t = eval(input("Enter the time interval between position calculations: "))
return a,v,h,t
def main():
angle, vel, h0, time = getInputs()
cball = Projectile(angle, vel, h0)
while cball.getY() >= 0:
cball.update(time)
print("\nDistance traveled: {0:0.1f} meters.".format(cball.getX()))
print("\nMaximum height traveled: {0:0.1f} meters.".format(cball.getMaxY()))
if __name__ == "__main__":
main()
其中代碼使用這個 – Ben
對不起，剛添加它。 – user3754248
調試提示。將update語句添加到update（）並觀察maxypos的值如何更改。 –