Question

在试图弄清楚BeautifulSoup是如何工作的时候，我偶然学会了__str__方法（我是python的新手）。因此，如果我没有误解，那么__str__方法有助于塑造如果打印出来，将如何表示类。例如：

class Foo:
    def __str__(self):
        return "bar"

>>> x = Foo()
>>> print x
bar

右？所以断言我是对的，是否可以覆盖字典列表的__str__方法？我的意思是说在Foo课你有：

class Foo:
   def __init__(self):
      self.l = [{"Susan": ("Boyle", 50, "alive")}, {"Albert": ("Speer", 106, "dead")}]

现在可以得到以下结果吗？

>>> x = Foo()
>>> print x.l
"Susan Boyle is 50 and alive. Albert Speer is 106 and dead."

修改

考虑到agf的解决方案，我该如何再次访问字典？我的意思是，如果我定义__str__方法，那么显然我应该定义其他东西来检索字典。请考虑以下示例：

class PClass(dict):
    def __str__(self):
        # code to return the result that I want 

class Foo:
    def __init__(self):
        self.l = PClass({"Susan": ["Boyle", ........ })

>>> x = Foo()
>>> print x.l 
# result that works great
>>> y = x.l["Susan"] # this would not work. How can I achieve it?

Answer 1

您需要将您正在打印的项目子类化。

from itertools import chain

class PrintableList(list): # for a list of dicts
    def __str__(self):
        return '. '.join(' '.join(str(x) for x in
            chain.from_iterable(zip((item[0], 'is', 'and'), item[1])))
                for item in (item.items()[0] for item in self)) + '.'

class PrintableDict(dict): # for a dict
    def __str__(self):
        return '. '.join(' '.join(str(x) for x in
            chain.from_iterable(zip((item[0], 'is', 'and'), item[1])))
                for item in self.iteritems()) + '.'

class Foo:
   def __init__(self):
      self.d = PrintableDict({"Susan": ("Boyle", 50, "alive"), 
                              "Albert": ("Speer", 106, "dead")})

class Bar:
   def __init__(self):
      self.l = PrintableList([{"Susan": ("Boyle", 50, "alive")}, 
                              {"Albert": ("Speer", 106, "dead")}])

foo = Foo()
print self.d
bar = Bar()
print self.l

Answer 2

另一种方法是覆盖__getattribute__，它允许您自定义返回属性的方式：

class Foo(object):
    def __init__(self):
        self.l = [{"Susan": ("Boyle", 50, "alive")}, {"Albert": ("Speer", 106, "dead")}]

    def __getattribute__(self, name):
        return PrintableList(l)
        attr = super(Foo, self).__getattribute__(name)
        items = sum([x.items() for x in attr], [])
        return ' '.join([' '.join([k, v[0], 'is', str(v[1]), 'and', v[2] + '.']) for k,v in items])

>>> f = Foo()
>>> print f.l
<<< Susan Boyle is 50 and alive. Albert Speer is 106 and dead.

Answer 3

您可以为您的Foo类定义__str__以返回您想要的内容：

class Foo():
    def __init__(self):
        self.l = [{"Susan": ("Boyle", 50, "alive")}, {"Albert": ("Speer", 106, "
dead")}]
    def __str__(self):
        ret_str = ""
        for d in self.l:
            for k in d:
                ret_str += "".join([k, " ", d[k][0], " is ", str(d[k][1]), " and
 ", d[k][2], ". "])
        return ret_str

foo = Foo()
print foo

结果：

Susan Boyle现年50岁。阿尔伯特施佩尔已经106岁了。

对象的python str

3 个答案:

对象的python __str__

3 个答案:

对象的python str