将函数或属性应用于相同 class 的多个方法

Question

在下面的示例中，class MyExample 读取文件名中包含下划线的文件名列表。

class MyExample(object):
    def __init__(self, location: str):
        self.location = location

    def get_file_names(self):
        # For simplicity, lets just return an example of the output
        return ["my_file_name_01.txt", "my_file_name_02.txt"]

    def get_file_name_number(self):
        # Idem as before. 
        return ["file_name_01.txt", "file_name_02.txt"]

    def get_file_size(self):
        # It does not return a list of strings so the desired 
        # property or function will not be applied here
        return [3800, 4000]

执行代码时，结果为

my_object = MyExample("./a/random/path")
print(my_object.get_file_names())
print(my_object.get_file_name_number())
print(my_object.get_file_size())

# The results:
['my_file_name_01.txt', 'my_file_name_02.txt']
['file_name_01.txt', 'file_name_02.txt']
[3800, 4000]

现在，我想找到一种方法来 应用一个函数或属性（我们称之为 to_dot），它可以替换下划线get_file_names() 和 get_file_name_number 输出的点。

最终代码应该 return 类似于

# Calling this function with .to_dots
my_object.get_file_names().to_dots
["my.file.name.01.txt", "my.file.name.02.txt"] # <-- The desired output

# Calling this function with .to_dots
my_object.get_file_name_number().to_dots
["file.name.01.txt", "file.name.02.txt"] # <-- The desired output

# Calling this function with .to_dots
my_object.get_file_name_number().to_dots
AttributeError #  # <-- The desired output ... or something similar

有没有办法将to_dots加到classMyExample中，以替换里面某些方法的下划线？
我对装饰器不是很熟悉，但我怀疑这样做可能有技巧。到目前为止，我尝试使用 @property 没有成功，但据我所知，有很多类型的装饰器......或者也许没有装饰器也可以完成，我很迷茫。谢谢。

Answer 1

定义你自己的装饰器：

def to_dots(func):
    def inner():
        original_return = func()
        return [item.replace('_','.') for item in original_return ]
    return inner

并将其用作：

@to_dots
def get_file_names(self):

Answer 2

你可以这样做：

from collections import UserList

class MyList(UserList):
    @property
    def to_dots(self):
        return [s.replace("_", ".") for s in self.data]

class MyExample(object):
    def __init__(self, location: str):
        self.location = location

    def get_file_names(self):
        return MyList(["my_file_name_01.txt", "my_file_name_02.txt"])

结果

my_object = MyExample("./a/random/path")
print(my_object.get_file_names())
print(my_object.get_file_names().to_dots)

是

['my_file_name_01.txt', 'my_file_name_02.txt']
['my.file.name.01.txt', 'my.file.name.02.txt']

Answer 3

为什么不将所需的输出格式（是否带点）作为可选参数传递给这些方法？

class MyExample(object):
    def __init__(self, location: str):
        self.location = location

    @staticmethod
    def map_list(lst, dotted=False):
        return [s.replace("_", ".") for s in lst] if dotted else lst

    def get_file_names(self, dotted=False):
        return self.map_list(["my_file_name_01.txt", "my_file_name_02.txt"], dotted)

    def get_file_name_number(self, dotted=False):
        return self.map_list(["file_name_01.txt", "file_name_02.txt"], dotted)

    def get_file_size(self):
        return [3800, 4000]

my_object = MyExample("./a/random/path")
print(my_object.get_file_names())  # Underscores untouched
print(my_object.get_file_name_number(dotted=True))  # Underscores replaced
print(my_object.get_file_size())

Answer 4

您可以使用 class 装饰器 将 函数装饰器 应用到指定的 class 方法。

from functools import wraps
import inspect


def dec_methods(decorator, *members):
    """Class decorator to apply specfied decorator to specified members of class."""

    def dec_the_class(cls):
        for name, m in inspect.getmembers(cls, inspect.isfunction):
            if name in members:
                setattr(cls, name, decorator(m))
        return cls
    return dec_the_class


def to_dots(func):
    """Function decorator to replace '_' with dots in list of strings returned."""

    @wraps(func)
    def wrapped(*args, **kwargs):
        results = func(*args, **kwargs)
        results = [result.replace('_', '.') for result in results]
        return results
    return wrapped


@dec_methods(to_dots, 'get_file_names', 'get_file_name_number')
class MyExample(object):
    def __init__(self, location: str):
        self.location = location

    def get_file_names(self):
        # For simplicity, lets just return an example of the output
        return ["my_file_name_01.txt", "my_file_name_02.txt"]

    def get_file_name_number(self):
        # Idem as before.
        return ["file_name_01.txt", "file_name_02.txt"]

    def get_file_size(self):
        # It does not return a list of strings so the desired
        # property or function will not be applied here
        return [3800, 4000]


my_object = MyExample("./a/random/path")
print(my_object.get_file_names())        # -> ['my.file.name.01.txt', 'my.file.name.02.txt']
print(my_object.get_file_name_number())  # -> ['file.name.01.txt', 'file.name.02.txt']
print(my_object.get_file_size())         # -> [3800, 4000]

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