如何最好地打印从用户定义的实例变量创建的字典？

Question

我正在尝试将我的奶牛整理到字典中，访问它们的值，并将它们打印到控制台。

奶牛的每个实例都分配给奶牛列表中的一个索引。

我正在尝试创建一个字典如下：

for i in cows:
    cowDict[i.getName] = (i.getWeight, i.getAge)

我希望能够使用我的牛名访问我的字典的值，即：

c["maggie"]

但是，我的代码产生了一个关键错误。

如果我打印整本词典，我会得到这样的结果：

"{<'绑定方法cow.getName of <'maggie, 3, 1>>: (<'绑定方法cow.getWeight of <'maggie, 3, 1>>, <' <'maggie, 3, 1>> 的绑定方法 cow.getAge), etc...}"

我可以用实例变量替换 .getName 并获得所需的结果，但是，有人建议我不要使用这种方法。

使用 cow 类型的实例变量创建字典的最佳做法是什么？

代码：

class cow(object):
    """ A class that defines the instance objects name, weight and age associated
        with cows
    """
    def __init__(self, name, weight, age):
        self.name = name
        self.weight = weight
        self.age = age
    def getName(self):
        return self.name
    def getWeight(self):
        return self.weight
    def getAge(self):
        return self.age
    def __repr__(self):
        result = '<' + self.name + ', '  + str(self.weight) + ', ' + str(self.age) + '>'
        return result

def buildCows():
    """
    this function returns a dictionary of cows
    """
    names = ['maggie', 'mooderton', 'miles', 'mickey', 'steve', 'margret', 'steph']
    weights = [3,6,10,5,3,8,12]
    ages = [1,2,3,4,5,6,7]
    cows = []
    cowDict = {}
    for i in range(len(names)):
        #creates a list cow, where each index of list cow is an instance 
        #of the cow class
        cows.append(cow(names[i],weights[i],ages[i]))
    for i in cows:
        #creates a dictionary from the cow list with the cow name as the key
        #and the weight and age as values stored in a tuple
        cowDict[i.getName] = (i.getWeight, i.getAge)
    #returns a dictionary
    return cowDict

c = buildCows()

Answer 1

getName 是一个函数所以尝试

for i in cows:
    cowDict[i.getName()] = (i.getWeight(), i.getAge())

Answer 2

你可以用类似的东西来简化它：

names = ['maggie', 'mooderton', 'miles', 'mickey', 'steve', 'margret', 'steph']
weights = [3,6,10,5,3,8,12]
ages = [1,2,3,4,5,6,7]

cows = {names[i]: (weights[i], ages[i]) for i in range(len(names))}

for name in names:
    print '<%s, %d, %d>' % (name, cows[name][0], cows[name][1])

输出：

<maggie, 3, 1>
<mooderton, 6, 2>
<miles, 10, 3>
<mickey, 5, 4>
<steve, 3, 5>
<margret, 8, 6>
<steph, 12, 7>

Answer 3

这看起来像是 zip 的工作。我们可以将它与字典推导结合使用，从任意键和值表达式创建字典，如下所示

{name: (weight, age) for name, weight, age in zip(names, weights, ages)}`

然后我们可以将 buildCows 重新定义为

def buildCows():
    names = ['maggie', 'mooderton', 'miles', 'mickey', 'steve', 'margret', 'steph']
    weights = [3,6,10,5,3,8,12]
    ages = [1,2,3,4,5,6,7]
    return {name: (weight, age) for name, weight, age in zip(names, weights, ages)}

Python 对 class 属性采取开放政策，因此默认情况下它们是 public，除非它们的名称前面有下划线或双下划线（双下划线）。通常不需要像在许多其他 OO 语言中那样创建 getters/accessor 方法。如果你真的想要私有实例变量，你可以阅读它们 here

dict 中错误结果的原因是它被填充了对函数的引用而不是调用它们（即 i.getWeight 应该是 `i.getWeight()

如何最好地打印从用户定义的实例变量创建的字典？

How to best print dictionaries created from user defined instance variables?

python

oop

dictionary

repr