Python lambda 返回值

Question

I'm learning the lambda options to return in python and i have a question:

I need to fill the returns in this function:

def func(n):
   if n==0:
      print("finished")
   else:
      return ___
func(5)()()()()()
func(3)()()()
func(8)()()()()()()()()

The output:

finished
finished
finished

I thought this one is a recursive call like return func(n-1) but it doesn't work, and throws an error. Is there an option to overcome the extra empty brackets? count them? do something, because it should be runnable.

Thanks

Answer 1

You're right about needing to use lambdas and func n-1, specifically

return lambda: func(n-1)

This returns a lambda that doesn't need any parameters passed in, to handle the brackets, and the return of the is the function being called with n-1, which in most calls you're making, is returning the next lambda function call

Answer 2

The operator () is the function call. So for example:

def foo():
   print('Foo executed')

def bar():
   # We return the foo FUNCTION itself, without calling it.
   return foo

In the above code, if you execute foo() , it'll print "Foo executed". But if you execute bar() , it will return foo , which is the function. So you can execute bar()() , where the first () is executing the function bar, returning foo, and then with the second (), you call the returned foo function.

Edit: When I typed it, you removed the what are those bunch of () because they are new to you... But I just leave it there maybe it'll help.