[英]Python shorthand for a tuple of a set of class attributes
Say i am using a class from some python package that looks like the following 假设我正在使用一些python包中的类,如下所示
class foo(object):
def __init__(self):
self.a = None
self.b = None
self.c = None
self.d = None
self.e = None
self.f = None
Now I need to use attributes b
, d
, and e
of object foobar of class foo in some operation, say call a function qux for instance: 现在我需要在某些操作中使用类foo的对象foobar的属性b
, d
和e
,例如调用函数qux:
print qux(foobar.b, foobar.d, foobar.e)
Is there any way to create a shorthand version of this, something like the following imagined code: 有没有办法创建这个的速记版本,如下面的想象代码:
print qux(*foobar.[b,d,e])
Note the constraints: neither the class nor the function can be changed. 注意约束:类和函数都不能改变。
Well, getattr
and setattr
get you close: 好吧, getattr
和setattr
让你关闭:
Assignment with setattr
(not needed for the next to work, just here for illustration): 使用setattr
分配(下一次工作不需要,只是为了说明):
class foo(object):
def __init__(self):
for name in 'abcdef':
setattr(self, name, None)
Using values with getattr
: 在getattr
使用值:
print qux(*(getattr(foobar, name) for name in 'bde'))
With normal, longer names you'd need to do in ['foo', 'bar']
instead. 使用正常的,更长的名称,你需要in ['foo', 'bar']
。
Since you can't modify the class, how about a function that takes an instance and any number of attribute names, and returns a tuple: 由于您无法修改类,因此获取实例和任意数量的属性名称的函数如何,并返回一个元组:
class Foo(object):
def __init__(self):
self.a = 1
self.b = 2
self.c = 3
def getitems(obj, *items):
values = []
for item in items:
values.append(getattr(obj, item))
return tuple(values)
f = Foo()
print getitems(f, 'a', 'c') # prints (1, 3)
qux(*getitems(f, 'a', 'c'))
If you are willing to modify the class, you can override __getitem__
to accept a tuple of keys. 如果您愿意修改该类,则可以覆盖__getitem__
以接受一组键。
class Foo(object):
def __init__(self):
self.a = 1
self.b = 2
self.c = 3
def __getitem__(self, item):
if isinstance(item, basestring):
# treat single key as list of length one
item = [item]
values = []
for key in item:
# iterate through all keys in item
values.append(getattr(self, key))
return tuple(values)
f = Foo()
print f['a', 'c'] # prints (1, 3)
qux(*f['a', 'c'])
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