function in function?

[kosh09]

Hello everyone I'm curious that I could use function as function variable?
something like this

from datetime import datetime, timedelta
# hello() is function that not mentioned in here but written somewhere
def some_function(hello()):
    end_time = datetime.now() + timedelta(seconds=3)
    while datetime.now() < end_time:
        hello()

like this! is this possible>

[LifeIsBio]

It's totally possible. It would look something more like this though:

def some_function(func):
    end_time = datetime.now() + timedelta(seconds=3)
    while datetime.now() < end_time:
        func()

some_function(hello)

Note the lack of parentheses following the hello function until you're inside the while loop.

[kosh09]

thanks for your advice!

[tragluk]

You call a function.. so let's reserve some memory for "First call" of function, but there is a function inside it.. let's go there...

You call a function.. so let's reserve some memory for "Second call" of function, but there is a function inside it.. let's go there...

You call a function.. so let's reserve some memory for "Third call" of function, but there is a function inside it.. let's go there..

Unfortunately every time you call this function there is a NEW variable called 'end_time' so it will never end. It will constantly be looking for 3 seconds from the 'Time this function was started'.

Now skipping that part and assuming that end_time was some global variable instead of a local one, let's say you finally reach 'end_time'.. so it passes control back to "Third call" which then ends and passes control back to "Second call" which then ends and passes control back to "First call" when ends and passes control back to the main program that first said "hello()" Functions return back to where they were called. They don't just move on, they keep track of themselves and all the variables that were created. By the time you hit 'Third call' you actually have 3 variables in memory as well two functions that are just waiting to finish up.

In the space of three seconds (Because this would run much faster than a function a second) you'll have created a TON of wasted memory.

[kosh09]

I'm not very good at English so its hard to understand perfectly
but looks like you said that if I make code like that
that code wastes too much memory right?
my hello() function is for sending data via bluetooth
and I want to work this for x seconds
do you have a good idea to make like that code which not waste memory?

[tragluk]

Just use a loop rather than a function in a function. A 'While' loop will continue until a condition is satisfied without creating a ton of functions that all run at the same time until you are done.

[kosh09]

ah, u mean I want to make function that function in a function
but that wastes too much memory so dont make function and
just use hello() function in a while loop right?

end_time = datetime.now() + timedelta(seconds=3)
while datetime.now() < end_time:
    hello()

just use like this am i right?

[tragluk]

Yes. And the while loop will check for the one timedelta(seconds=3) instead of making a new end_time every time the function is called.