[Benjamin Peterson]

I've found as I write more and more decorators I need an identity function often. For example I might write:

def replace_maybe(reason): if reason == "good reason": return lambda x: x def decorator(func): # do fancy stuff here return decorator

I hate lambdas, so usually I write

def _id(x): return x

It'd be nice to have a shortcut in the stdlib, though. Would this go well in the operator or functools modules well?

-1 I and Paul Rubin considered this a long time ago. It stayed on the todo list for a while and then fell by the wayside as its downsides became apparent. One problem is that many of the places whether it is tempting to use an identity function, it is just a slower way to do something that we should have used a simple if-statement for. In your example, there is no cost, but it is terrible to end-up with variants of map(func, iterable) where func defaults to lambda x: x. The other issue is that different signatures were needed for different tasks. identity = lambda *args: args identity = lambda *args: args[0] if args else None identity = lambda x: x Better to let people write their own trivial pass-throughs and think about the signature and time costs. Raymond

[Benjamin Peterson]

I've found as I write more and more decorators I need an identity function often. For example I might write:

def replace_maybe(reason): if reason == "good reason": return lambda x: x def decorator(func): # do fancy stuff here return decorator

I hate lambdas, so usually I write

def _id(x): return x

It'd be nice to have a shortcut in the stdlib, though. Would this go well in the operator or functools modules well?

-1 I and Paul Rubin considered this a long time ago. It stayed on the todo list for a while and then fell by the wayside as its downsides became apparent. One problem is that many of the places whether it is tempting to use an identity function, it is just a slower way to do something that we should have used a simple if-statement for. In your example, there is no cost, but it is terrible to end-up with variants of map(func, iterable) where func defaults to lambda x: x. The other issue is that different signatures were needed for different tasks. identity = lambda *args: args identity = lambda *args: args[0] if args else None identity = lambda x: x Better to let people write their own trivial pass-throughs and think about the signature and time costs. Raymond