Apply multiple methods to a single object?

Question

While saving outputs in a data structure to check posteriorly. The methods return strings (parsing or selecting HTML, they don't modify the object).

I've found a "hard-coded" solution by creating a class which is not very motivating for now: call list of function using list comprehension.

[Maybe another Library for checking libraries would be an extreme. I tried to put a few print in Python source but it didn't obey me. It seems that another instance is running]

I've tried this syntax (not possible):

result = [obj.f() for f in [append, attrs]]

because append and attrs aren't static functions by default but 'dotted' as showed above.

The goal is just a simple check of all obj methods.

[edits are highly recommended]

Update

In [122]: getattr? Docstring: getattr(object, name[, default]) -> value

Get a named attribute from an object; getattr(x, 'y') is equivalent to x.y. When a default argument is given, it is returned when the attribute doesn't exist; without it, an exception is raised in that case. Type: builtin_function_or_method getattr(): attribute name must be string Only 2 works. It is the "result" to get (not hard-coding it) More information for 'model' as an object.

You could do `result = [f() for f in [obj.append, obj.attrs]]` or `result = [getattr(obj, f)() for f in ["append", "attrs"]]` — kindall, Apr 24 '19 at 21:00
I've tried it, and I updated as a result. It seems that I missed attributes, which I am not figured out yet. — Alekssandro Assis Barbosa, Apr 25 '19 at 00:01

score 1 · Answer 1 · answered Apr 24 '19 at 21:02

You want either bound methods:

result = [f() for f in [obj.append, obj.attrs]]

or dynamic attribute lookup via either getattr:

result = [getattr(obj, m)() for m in ["append", "attrs"]]

If you plan to do this for a lot of objects, you might want to use operator.methodcaller:

methods = [methodcaller(m) for m in ["append", "attrs"]]
results_for_obj_a = [f(obj_a) for f in methods]
results_for_obj_b = [f(obj_b) for f in methods]
# etc.

methodcaller is a way of abstracting the idea of calling a method away from any particular object.

methodcaller(method_name)(obj) == getattr(obj, method_name)()

I wrote a methodcaller like these, but getattr expects strings, and not an 'undefined function name' as I pointed. When I use those functions, the object returns Dict sometimes. 'Object' is a parsed HTML from BeautifulSoup's call of html.parser. — Alekssandro Assis Barbosa, Apr 25 '19 at 00:06

Apply multiple methods to a single object?

1 Answers1