Question

所以我创建了一个非常简单的温度等级，它可以将给定温度从摄氏温度转换为华氏温度，反之亦然。问题是我希望有一个＆＃34;转换＆＃34;如果直接调用则执行的类中的方法，但如果被赋值给变量则不会执行。这是我的代码：

class Temperature:
    def __init__(self,temp=None,cf='C'):
        if temp == None:
            self.temp = float('0.0')
        else:
            try:
                self.temp = float("{0:.2f}".format(temp))
            except:
                print('Your temperature must be a number!')              
        if cf not in ['c','C','f','F']:
            print('You must identify the temperature as either F for Fahrenheit or C for Celsius!')
        else:
            self.cf = cf.upper()
    def convert(self):
        if self.cf == 'F':
            self.temp = float("{0:.2f}".format((self.temp - 32) * 5 / 9))
            self.cf = 'C'
            return(self)
        elif self.cf == 'C':
            self.temp = float("{0:.2f}".format((9/5)*self.temp + 32))
            self.cf = 'F'
            return(self)
    def __repr__(self):           
        return('Temperature({},{})'.format(self.temp,self.cf))

结果：

>>>t1 = Temperature()
>>>t1
Temperature(0.0,C)
>>>t2 = Temperature(100,'f')
>>>t2
Temperature(100.0,F)
>>>t3 = t3 = Temperature('12.5','c')
>>>t3
Temperature(12.5,C) #works fine up to here

>>>t1.convert()
Temperature(32.0,C) #converts when called - just what I want
>>>t4 = t1.convert() #Should set t4 equal TO VALUE of 't1.convert()' without rerunning method
>>>t4
Temperature(0.0,C) #THIS IS WHERE I GET LOST. I want t4 to print out 'Temperature(32.0,C)' Ideas?

Answer 1

一种方法是创建Temperature的新实例，并为其转换值，而不修改Temperature当前实例的值：

    def convert(self):
        if self.cf == 'F':
            return Temperature(float("{0:.2f}".format((self.temp - 32) * 5 / 9)), 'C')
        elif self.cf == 'C':
            return Temperature(float("{0:.2f}".format((9/5)*self.temp + 32)))

结果：

>>>t1 = Temperature()
>>>t1
Temperature(0.0,C)
>>>t1.convert()
Temperature(32.0,C)
>>>t1
Temperature(0.0,C)
>>>t4 = t1.convert()
>>>t4
Temperature(32.0,C)

Answer 2

考虑到这一点，当您再次致电t1.convert()时，它会更改self.cf值，所以下次运行 if 条件并返回Instance。

t1 = Temperature()

print t1.convert()
print '======='
print t1.convert()
print '======='
t4 = t1.convert()
print t4

输出： -

C
Temperature(32.0,F)
=======
F
Temperature(0.0,C)
=======
C
Temperature(32.0,F)

Answer 3

也许你可以做这样的事情？

class TemperatureError(Exception):
    pass


class Temperature(object):
    def __init__(self, temp=None, scale='C'):
        self._celcius = None
        self._fahrenheit = None
        if temp:
            if scale in ('c', 'C'):
                self.celcius = temp
            elif scale in ('f', 'F'):
                self.fahrenheit = temp
            else:
                raise TemperatureError

    @property
    def celcius(self):
        return self._celcius

    @celcius.setter
    def celcius(self, temp):
        self._celcius = float('{0:.2f}'.format(temp))
        self._fahrenheit = float('{0:.2f}'.format((temp - 32) * 5 / 9))

    @property
    def fahrenheit(self):
        return self._fahrenheit

    @fahrenheit.setter
    def fahrenheit(self, temp):
        self._celcius = float('{0:.2f}'.format(temp * 9 / 5 + 32))
        self._fahrenheit = float('{0:.2f}'.format(temp))

结果如下：

>>> t = Temperature(20, 'F')
>>> t.fahrenheit
20.0
>>> t.celcius
68.0

在Python中创建一个变量并将其分配给函数的最后一次调用，而无需再次调用该函数

3 个答案: