what am i doing wrong with __str__ in python ?

[Jonathan_26]

So for this program im trying to print out the max height the projectile reaches and when i run the str on the object it dosent change the value to the string and just gives a garbage result. the program als o prints some other vaulues but my problem is with the max height portion

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)
    def update(self, time):
        """Update the state of this projectile to move it time seconds farther into its flight"""
        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 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 maxHeight():
    time=self.yvel/9.8
    self.maxheight=self.ypos+time*(self.yvel/2.0)
    return self.maxheight  
def __str__():
    return str(maxHeight)
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("\nMaximun height:" + str(maxHeight) + " meters")
if __name__ == "__main__":
    main()

this returns
Distance traveled: 232.5 meters.

Maximun height:<function maxHeight at 0x05A2E9C0> meters

input
Enter the launch angle (in degrees): 60
Enter the initial velocity (in meters/sec): 50
Enter the initial height (in meters): 20
Enter the time interval between position calculations: 0.1

[rproffitt]

I'm a Python beginner but line 36 looks to missing it's self. to the the variable.

Line 43 seems to have a similar issue so my view is maxHeight() is one object and self.maxHeight is a value.
So line 43 might be as follows once line 36 is fixed to be:
print("\nMaximun height:" + Projectile() + " meters")

Why?

print will automatically call str() on the object and as such use the type’s str method to convert it to a string.

Sorry if I mislead you but I'm just a Python beginner too.

[vmanes]

First, your maxHeight needs to be a member of the class, so move it up. And it needs self as a parameter, like:

    def getX(self):
        "Returns the x position (distance) of this projectile."
        return self.xpos
    def maxHeight(self):
        time=self.yvel/9.8
        self.maxheight=self.ypos+time*(self.yvel/2.0)
        return self.maxheight

Then your problem with str( ) needs two fixes. As is, you asking to convert the function to a string, not its return value. You also need to append it class object. Like:

    print("\nMaximun height:" + str(cball.maxHeight() ) + " meters")

I'm not sure the purpose of your __str__() function.