如何在Python中按顺序打印为类创建的所有变量的列表？

Question

我有以下课程:

class Countries(object):
    def __init__(self, country_capital, country_population):
        self.capital = country_capital
        self.population = country_population

以及连接到类的变量列表:

france = Countries("Paris", "66")
england = Countries("London", "53")
usa = Countries("Washington, DC", "318")
germany = Countries("Berlin", "80")

我如何按人口顺序查看国家()首都？例如["伦敦","巴黎","柏林","华盛顿特区"]

Answer 1

将您的类放在一个列表中,并根据population属性(必须转换为整数才能正确排序)对它们进行排序:

[c.capital for c in sorted([france, england, usa, germany], key=lambda c: int(c.population))]

这将使用列表解析提取只是从每个国家物体首都名,按人口排序的对象后.

我使用函数的key参数告诉它对属性进行排序(转换为数字):sorted()Countries.populationint()

>>> class Countries(object):
...     def __init__(self, country_capital, country_population):
...         self.capital = country_capital
...         self.population = country_population
...
>>> france = Countries("Paris", "66")
>>> england = Countries("London", "53")
>>> usa = Countries("Washington, DC", "318")
>>> germany = Countries("Berlin", "80")
>>> [c.capital for c in sorted([france, england, usa, germany], key=lambda c: int(c.population))]
['London', 'Paris', 'Berlin', 'Washington, DC']

或者你可以,你知道,手动将它们按顺序排列,但我认为你想让计算机进行排序.. :-)