Python函数总是返回相同的布尔值

Question

In functional programming is sometimes useful to have a function that always return True (or False ) for every parameter (or even multiple parameters).

Is there a built-in or a function defined in some module that have this exact behaviour?

Answer 1

I'm not aware of any built-in, but you can define them as:

false = lambda *_: False
true  = lambda *_: True

Answer 2

You can use object , since its instances will always be treated as a true value, since object defines neither __len__ , __nonzero__ (in Python 2), nor __bool__ (in Python 3).

>>> bool(object())
True
>>> if object():
...   print("Hi")
...
Hi