I feel I'm shaky on understanding the interplay between passing variables through functions (outside of classes)...Basically IDK when to use foo() vs foo(bar) especially in freestanding (OUTSIDE of a class) nested functions.

PLEASE HELP

I wrote this up. it's a self contained script:

#!usr/bin/env python3 #defexp0.py import sys from functools import partial as p def inquire(a,type,errmsg):	while True:	b = input(a)	if b !='':	try:	b == type(b)	except ValueError:	print('{}'.format(errmsg))	continue	else:	print('ok')	return b	else:	print(f'{a:^50} must be answered.')	continue the_q = p(inquire,type=str,errmsg='sorry') def foo():	while True:	quit_now = the_q('\'y\' to quit anything else to continue')	quit_now.strip().lower()	if quit_now =='y' or quit_now =='yes':	sys.exit()	else:	bar()	continue def bar():	quest=the_q('please enter a, b, c, d or etc.')	quest.strip().lower()	if quest == 'a':	forA(quest)	elif quest == 'b':	forB()#won't work	elif quest == 'c':	forC(quest)	elif quest == 'd':	forD()	elif quest == 'e':	forE(quest)	else:	forEtc() def forA(x):	print(f'{x:^10}is fine.') def forB():	global someVariable	print('nothing...'.format(someVariable)) '''but this WOULD work: def forB():	global someVariable	print('nothing...') I don't understand ''' def forC(y):	print('{} works too...'.format(y)) def forD():	print('fine') def forE(someVariable):	global quest	print('should work...'.format(someVariable))	#forE() global variable names must be different from parameter names??? def forEtc():	print('works') if __name__=='__main__':	foo() else:	print('sorry {__name__} not main') 

It works. Except for [input]b[/input]

this triggers

Error:
Traceback (most recent call last): File "defexp0.py", line 77, in <module> foo() File "defexp0.py", line 30, in foo bar() File "defexp0.py", line 39, in bar forB()#won't work File "defexp0.py", line 54, in forB print('nothing...'.format(someVariable)) NameError: name 'someVariable' is not defined

Perhaps someone could clarify foo() vs foo(bar) and their nuances in nested functions? Please?

Think of a function as a sort of black box. You give it some data to work with, it does *something*, and then gives you a return value. A function shouldn't use any value that isn't passed to it. global should be avoided at all costs.

(Feb-24-2018, 06:13 PM)nilamo Wrote: Think of a function as a sort of black box. You give it some data to work with, it does *something*, and then gives you a return value.

Yes. And it works wonderfully well when functions are part of a class.

Quote:A function shouldn't use any value that isn't passed to it.

this is where I get frustrated lol. Pls see code in op above. Entire script runs off foo(). Not a single parameter, but quite a few variable gets assigned values in its body....
So this is what keeps getting me and textbooks seems to not care about the discrepency

def foo(): a = 'moo' print(a) bar() def bar(): print('bar function') if __name__=='__main__': foo() else: print('choosing not to run')

this script runs...this bothers me.

Maybe it's a detail that comes from experience but I never feel certain when I can make do with foo() and when I need foo(param)....

(Feb-24-2018, 09:14 PM)mepyyeti Wrote: this script runs...this bothers me.

Maybe it's a detail that comes from experience but I never feel certain when I can make do with foo() and when I need foo(param)....

Make it clear that foo takes a augment.

def foo(bar): a = 'moo' print(a) bar() def bar(): print('bar function') if __name__=='__main__': foo(bar) else: print('choosing not to run')

Quote:this is where I get frustrated lol. Pls see code in op above. Entire script runs off foo().

That's normal to have a function that run whole script,the design bit can be the hard part to figure out.
Clearer name(like eg menu) and never ever global,make it clear that a function take arguments,not to long functions.
Can be some tips.

Example no variables in global name namespace,calling menu start it.
result function takes 2 argumet,coin_flip and user_choice these function do only one task each.
Always fall back to menu where can play again or Quit out.

import random def coin_flip(): return random.choice(('head', 'tail')) def user_choice(): command = input("Choose Head or Tail: ").lower() return command def result(coin_flip, user_choice): ''' Doc string explain what function do''' coin = coin_flip() choice = user_choice() if coin == choice: print(f'\nComputer <{coin}> You gussed <{choice}> which is correct\n') else: print(f'\nComputer <{coin}> You gussed <{choice}> which is wrong\n') def menu(): while True: print('(1) Coin flip game') print('(Q) Quit\n') choice = input('Enter your choice: ').lower() if choice == '1': result(coin_flip, user_choice) elif choice == 'q': return False else: print(f'Not a correct choice: {choice}') if __name__ == '__main__': menu()

If function get to complicated to design use a class

SO with the 1st snippet:

def foo(bar): a = 'moo' print(a) bar() def bar(): print('bar function') if __name__=='__main__': foo(bar) else: print('choosing not to run')

since both foo() and foo(bar) work to execute the script...is it simply a matter of best practices to just use foo(bar) to run the script? Technically, whether or not I have a parameter doesn't seem too matter...

Regarding the snippet you wrote:

import random def coin_flip(): return random.choice(('head', 'tail')) def user_choice(): command = input("Choose Head or Tail: ").lower() return command def result(coin_flip, user_choice): ''' Doc string explain what function do''' coin = coin_flip() choice = user_choice() if coin == choice: print(f'\nComputer <{coin}> You gussed <{choice}> which is correct\n') else: print(f'\nComputer <{coin}> You gussed <{choice}> which is wrong\n') def menu(): while True: print('(1) Coin flip game') print('(Q) Quit\n') choice = input('Enter your choice: ').lower() if choice == '1': result(coin_flip, user_choice) elif choice == 'q': return False else: print(f'Not a correct choice: {choice}') if __name__ == '__main__': menu()

user_choice() clearly creates a variable, command, and gives it a value but necessitates no parameter. Yet, result(*args) also creates variables,coin and choice, and gives them the returned value of the 2 executed functions, coin_flip and user_choice.

why not just say:

... def result(): ''' Doc string explain what function do''' coin = coin_flip() choice = user_choice() ...

the logic works fine for

... def user_choice(): #yes I know value of command is set to user's input not the return result of a previous function command = input("Choose Head or Tail: ").lower() return command ...

Question boils down to : Why do I need to set up parameters at all. user_choice() shows that I can create variables without parameters (technically just 1 positional)? this is where I get tripped up...

(Feb-25-2018, 03:48 AM)mepyyeti Wrote: Why do I need to set up parameters at all. user_choice() shows that I can create variables without parameters

To make it clear and more readable that a function take in code in from outside.
The black box model as @nilamo talk abot crash as son as a function,variable,list,ect... magically appear in a function when is not set as parameter.
As soon as this happen you wonder where dos it come from has it a relationship with this function?
It can be easy to see in shorter code as my example,in larger code it can be a pain that stuff just magically appear from somewhere else.