如何询问 python 对象的结构? [英] How to interrogate a python object about its structure?

问题描述

有没有办法以编程方式确定对象的结构/模型、它的组成部分、如何对其进行迭代、操作和转换、分解和重新构建?

Is there a way to programmatically determine an object's structure/model, it's constituent parts, how it can be iterated and manipulated and transformed, broken down and built back up?

反复试验是伟大的老师.我每天都上他们的课.但在这里，我正在寻找一种更聪明地工作"或至少以不同方式工作的方法.

Trial and error are great teachers. I take their classes every day. But here I'm looking for a way to "work smarter" or at least differently.

一点背景知识:我最近花了太多时间来错误地处理熊猫 groupby 对象，因为我不了解它的组成部分和类型.我没有正确处理在 groupby 对象上迭代时返回的元组.我现在对这个特定对象的理解稍微好一点，但还不够充分:例如，一个 groupby obj 分解为 "params" 和 "table" 迭代时.table 依次由 index 和 rows 组成.但我仍然不确定如何处理 rows:它们由什么组成或分解成什么.这篇文章包含重现问题的代码:请参阅原始文章底部的编辑 2.

A little background: I recently spent way too many hours incorrectly handling a pandas groupby object because I did not understand the building block parts and types that it is made of. I did not correctly handle the tuple that is returned when iterating on a groupby object. I now have a slightly better, but not at all sufficient, understanding of this particular object: e.g., a groupby obj breaks down into "params" and "table" when iterated. table, in turn, is made up of index and rows. But I'm still not sure how to handle rows: what they're made of or break down into. This post includes code to reproduce the issue: see Edit 2 at the bottom of original post.

但这是一个特例；我的问题更笼统.我的问题是，如果我还不知道 python 对象/类型的结构或模型"，我如何查询对象以文本方式或图形方式显示此信息?

But this is a particular case; my question is more general. My question is, if I don't already know the structure or "model" of a python object/type, how can I query the object to reveal this information textually or, even better perhaps, graphically?

编辑:

出于探索和学习的目的，下面我尝试通过 for 循环在 str 对象上运行每个 str 方法.meth obj 在循环的前两行(例如，__add__ 和 __class__)中被正确解释，但被解释为 meth 当我尝试运行 obj.meth 时.我该如何解决这个问题?

For purposes of exploration and learning, below I try to run every str method on a str object via a for loop. The meth obj is interpreted correctly in the first two lines of the loop (e.g., __add__ and __class__), but is interpreted as meth when I try to run obj.meth. How can I fix this?

输入:

obj = 'my_string'

object_methods = [method_name for method_name in dir(obj)
                  if callable(getattr(obj, method_name))]

print(len(object_methods))
print(object_methods)

输出:

77
['__add__', '__class__', . . ., 'upper', 'zfill']

输入:

for meth in object_methods:
    print(meth)
    try:
        print('obj.meth for obj', obj, 'and method', meth, ':') 
        obj.meth
    except AttributeError as e:
        print('obj.meth for obj', obj, 'and method', meth, ': AttributeError:', e)

输出:

__add__
obj.meth for obj my_string and method __add__ :
obj.meth for obj my_string and method __add__ : AttributeError: 'str' object has no attribute 'meth'
__class__
obj.meth for obj my_string and method __class__ :
obj.meth for obj my_string and method __class__ : AttributeError: 'str' object has no attribute 'meth'
. . .

推荐答案

您可以使用 __dict___ 和 dir 以查看对象模型.

You can use __dict___ and dir in order to see object model.

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

jack = Person('jack',23)
print(jack.__dict__)
print(dir(jack))

输出:

{'age': 23, 'name': 'jack'}
['__doc__', '__init__', '__module__', 'age', 'name']

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