可赎回的断言？ [英] Callable assertion?
问题描述
我有一个函数可以通过回调函数作为
参数。我想检查以确保传入的内容确实可以调用
。是：
断言''__call__''在dir（param）
正确的做法，还是有更清洁的东西？对于param的所有可调用值，它是否会工作
，无论它是静态函数，
类方法，内置等等？
我正在运行2.3.1。对于我来说，向后兼容性并不是特别的问题
，但我想知道这个
的工作时间有多久会很好。
I''ve got a function which gets passed a call-back function as a
parameter. I want to check to make sure the thing passed in is indeed
callable. Is:
assert ''__call__'' in dir (param)
the right thing to do, or is there something cleaner? Will that work
for all callable values of param, regardless if it''s a static function,
class method, built-in, etc?
I''m running 2.3.1. Backward compatability isn''t particularly an issue
for me, but I guess it would be nice to know how far back in time this
works.
推荐答案
On Sun，05 Oct 2003 08:55:45 -0400，
Roy Smith< ro*@panix.com>写道：
On Sun, 05 Oct 2003 08:55:45 -0400,
Roy Smith <ro*@panix.com> wrote:
正确的事情，还是有更清洁的东西？这对于param的所有可调用值是否有效，无论它是静态函数，类方法，内置等等？
the right thing to do, or is there something cleaner? Will that work
for all callable values of param, regardless if it''s a static function,
class method, built-in, etc?
有一个可调用的（param）内置函数，可以追溯到Python 1.2。
--amk
There''s a callable(param) built-in function, dating back to Python 1.2.
--amk
文章< wM ******************** @ speakeasy.net>，
" AM了Kuchling" < am*@amk.ca>写道：
In article <wM********************@speakeasy.net>,
"A.M. Kuchling" <am*@amk.ca> wrote:
On Sun，05 Oct 2003 08:55:45 -0400，
Roy Smith< ro*@panix.com>写道：
On Sun, 05 Oct 2003 08:55:45 -0400,
Roy Smith <ro*@panix.com> wrote:
正确的事情，还是有更清洁的东西？这对于param的所有可调用值是否有效，无论它是静态函数，类方法，内置等等？
the right thing to do, or is there something cleaner? Will that work
for all callable values of param, regardless if it''s a static function,
class method, built-in, etc?
'可调用（param）内置函数，可追溯到Python 1.2。
- amk
There''s a callable(param) built-in function, dating back to Python 1.2.
--amk
啊。这正是我想要的！文档说：
"如果对象参数显示为可调用，则返回true，否则返回false。如果
返回true，则调用仍然可能失败，但如果它是
false，则调用object将永远不会成功。
看似可调用的是什么意思？在什么情况下
callable（foo）返回True，但foo（）会失败？
Ah. That''s exactly what I was looking for! The docs say:
"Return true if the object argument appears callable, false if not. If
this returns true, it is still possible that a call fails, but if it is
false, calling object will never succeed."
What does "appears callable" mean? Under what circumstances would
callable(foo) return True, yet foo() would fail?
" ;罗伊史密斯 < ro*@panix.com>在消息中写道
news：ro *********************** @ reader2.panix.com ..。
"Roy Smith" <ro*@panix.com> wrote in message
news:ro***********************@reader2.panix.com.. .
我有一个函数可以将回调函数作为
参数传递。我想检查以确保传入的内容是
确实可以调用。
I''ve got a function which gets passed a call-back function as a
parameter. I want to check to make sure the thing passed in is indeed callable.
酸测试是尝试调用它：
try：param（）
除了TypeError，msg：<做什么>
你可以查看msg.endswith（' 'not callable''）如果你想要，但是我不知道错误信息的稳定性。
Terry J. Reedy
The acid test is to try calling it:
try: param()
except TypeError, msg: <do whatever>
You can check that msg.endswith(''not callable'') if you want but I
don''t know the stability of the error message.
Terry J. Reedy
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