How can a function takes another function WITH arguments, as a parameter?

Question

def Wrapper(func):
  def MyPrint(message):
    print('Hello ' + message)
  
  func(MyPrint)

Wrapper(lambda my_print: my_print('world'))

I'm confused of the above code. I get that a function can take another function as parameter and use func() to invoke it, but how can Wrapper(lambda my_print: my_print('world')) call the inner function MyPrint? The func is a parameter, and the lambda my_print: my_print('world') is its argument, but somehow the argument seems to utilizes (penatrate through) an inner function inside Wrapper.

This is a very common pattern in JavaScript but confuses me. I think an explaination of what happened in detail might help.

Answer 1

(lambda my_print: my_print('world') doesn't call MyPrint directly; MyPrint is passed as its argument in func(MyPrint).

Try the substitution method:

Wrapper(lambda my_print: my_print('world'))

---> func is bound to lambda my_print: my_print('world') in the body of Wrapper:

def MyPrint(message):
    print('Hello ' + message)
  
  (lambda my_print: my_print('world'))(MyPrint)

--->

my_print is bound to MyPrint in the body of the lambda:

def MyPrint(message):
    print('Hello ' + message)
  
  MyPrint('world')

---

Addendum: the same, but with a non-local function and no lambda, in case that makes it clearer:

def GreetingPrinter(message):
    print('Hello ' + message)

def Wrapper(func):
  func(GreetingPrinter)

def PrintWithWorld(printer):
    printer('World')

Wrapper(PrintWithWorld)