python 2.7实例化另一个类中的类

Question

I am writing a class, Tbeam (Python 2.7.8 in IPython notebook 2.2.0) that calculates values for a reinforced concrete T beam. The flange and web of the Tbeam are considered to be objects of the class Rectangle. I instantiate a flange and web from the class Rectangle in the class Tbeam, and create methods to calculate the overall depth (d) and area (area) of the Tbeam.

class Rectangle:
"""A class to create simple rectangle with dimensions width (b) and 
height (d). """

def __init__(self, b, d ):
    """Return a rectangle object whose name is *name* and default
    dimensions are width = 1, height = 1.
    """
    self.width = b
    self.height = d

def area(self):
    """Computes the area of a rectangle"""
    return self.width * self.height

def inertia(self):
    """Computes the moment of inertia of a rectangle,
    with respect to the centroid."""

    return self.width*math.pow(self.height,3)/12.0

def perim(self):
    """Calculates the perimeter of a rectangle"""
    return 2*(self.width+self.height)

def centroid(self):
    """Calculates the centroid of a rectangle"""
    return self.height/2.0

def d(self):
    """Returns the height of the rectangle."""
    return self.height

def bf(self):
    """Returns the width of the rectangle."""
    return self.width

-

class Tbeam:

"""A class to create T beams with dimensions:
bf = width of top flange,
tf = thickness of top flange,
d = height of web,
bw = width of web. """

def __init__(self, bf,tf,d,bw):
    self.bf = bf
    self.tf = tf
    self.d = d
    self.bw = bw
    self.flange = Rectangle(bf,tf)
    self.web = Rectangle(bw,d)

def area(self):
    area =self.flange.area + self.web.area

def d(self):
    """Returns the total height of the Tbeam"""
    return self.flange.d + self.web.d

-

When I execute the test cell

# Test Tbeam
t1 = Tbeam(60.0, 5.0,27.0,12.0)
print t1.d
print t1.area

-

I get the following:

27.0

bound method Tbeam.area of <__main__.Tbeam instance at 0x7f8888478758

27.0 is correct but I do not understand the second response for print t1.area. I assume my definition for area is incorrect but I don't know how to correct the problem.

Many thanks

Ron

Answer 1

You're printing t1.area which is a method. You want to print the result of calling the method, so print t1.area() .

Answer 2

area method is defined as

def area(self):
    area =self.flange.area + self.web.area

but should be defined as

def area(self):
    area =self.flange.area() + self.web.area()