问题
I would like to call a method to give me a dict of all of the "non-private" (I use the term "private" somewhat loosely here since it does not really exist in Python) and non-builtin attributes (i.e. those that do not begin with a single or double underscore) on a class. Something like vars(MyClass) that would return only the "public" attributes on that class.
I'm aware that
from M import *
does not import objects whose name starts with an underscore. (http://www.python.org/dev/peps/pep-0008/#id25) How does import implement that? Via a builtin function or just by checking for underscores? What is the pythonic way to do this?
Example:
class MyClass(object):
def __init__(self):
do_stuff()
def _private(self):
print 'private'
def __gets_name_mangled(self:
print 'becomes _MyClass__gets_name_mangled()'
def public(self):
print 'public'
If I do
vars(MyClass).keys()
I get
['_MyClass__gets_name_mangled', '__module__', '_private', '__doc__', '__dict__', '__weakref__', 'public', '__init__']
How can I get only
['public']
Or do I just need to check for underscores myself? It just seems like there would be a pythonic way to do this.
For more on underscores and double underscores, see: What is the meaning of a single- and a double-underscore before an object name?
回答1:
With a dict comprehension that filters vars()
{ k:v for k,v in vars(myObject).items() if not k.startswith('_') }
Moved into a function that returns a list of attributes that are not 'soft private' or callables. You can return values if you like by changing to dict comprehension as above
def list_public_attributes(input_var):
return [k for k, v in vars(input_var).items() if
not (k.startswith('_') or callable(v))]
回答2:
Actually, it would be unpythonic for such function to exists - because "officially" there is no private or protected fields/properties in Python.
While it makes sense to throw away module attributes with leading underscores (which are usually some implementation details) during import *
from some module*, it is not useful in context of any other object.
So, if you need to list only "public" methods/attributes of an object, just iterate through result of dir
and drop names with leading underscores.
* "during import *
from some module'"
Usually it is not the best practice. Consider the next example:
module A
has a1
and a2
defined
module B
has b1
and b2
defined
This code in module C
works as expected:
from A import a1, a2
from B import *
Imagine we add function a1
in module B
. Now suddenly module C
is broken, although we haven't touched it.
回答3:
I'm using this function:
def print_all_public_fields(obj):
print(obj)
for a in dir(obj):
if not a.startswith('_') and not a.isupper():
print('\t%s = %s' % (a, getattr(obj, a)))
I know it's not exactly what you want, but maybe it'll give you some idea.
来源:https://stackoverflow.com/questions/17075071/is-there-a-python-method-to-access-all-non-private-and-non-builtin-attributes-of