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Groups > comp.lang.python > #101605 > unrolled thread

local variable 'juveniles' referenced before assignment

Started byAlan Robinson <arobinson@lordlawson.org.uk>
First post2016-01-13 04:23 -0800
Last post2016-01-13 05:26 -0800
Articles 7 — 3 participants

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  local variable 'juveniles' referenced before assignment Alan Robinson <arobinson@lordlawson.org.uk> - 2016-01-13 04:23 -0800
    Re: local variable 'juveniles' referenced before assignment Chris Angelico <rosuav@gmail.com> - 2016-01-13 23:32 +1100
      Re: local variable 'juveniles' referenced before assignment Alan Robinson <arobinson@lordlawson.org.uk> - 2016-01-13 04:54 -0800
        Re: local variable 'juveniles' referenced before assignment Chris Angelico <rosuav@gmail.com> - 2016-01-14 00:05 +1100
        Re: local variable 'juveniles' referenced before assignment Peter Otten <__peter__@web.de> - 2016-01-13 14:05 +0100
          Re: local variable 'juveniles' referenced before assignment Alan Robinson <arobinson@lordlawson.org.uk> - 2016-01-13 05:22 -0800
            Re: local variable 'juveniles' referenced before assignment Alan Robinson <arobinson@lordlawson.org.uk> - 2016-01-13 05:26 -0800

#101605 — local variable 'juveniles' referenced before assignment

FromAlan Robinson <arobinson@lordlawson.org.uk>
Date2016-01-13 04:23 -0800
Subjectlocal variable 'juveniles' referenced before assignment
Message-ID<d668ec4e-509e-48a4-9be5-017077629c6c@googlegroups.com>
def menu():
    option = int(input("Please select an option: \n 1: Set Generation 0 Values \n 2: View Generation 0 Values \n 3: Run Model \n 4: Print values"))

    if option == 1:
        juveniles,adults,seniles = setGen()
    elif option == 2:
        displayGen()
    elif option == 3:
        runModel(juveniles,adults,seniles)
    elif option == 4:
        print(juveniles,adults,seniles)
    menu()


def setGen():
    #enter number of juveniles
    juveniles = int(input("How many juveniles are in the total popluation?"))
    #enter number of adults
    adults = int(input("How many Adults are in the total popluation?"))
    #enter number of seniles
    seniles = int(input("How many Seniles are in the total popluation?"))
    #enter juvenilesenile survival rates
    return(juveniles,adults,seniles)
menu() 
when I go to print I get the above error I can't see a solution please help

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#101606

FromChris Angelico <rosuav@gmail.com>
Date2016-01-13 23:32 +1100
Message-ID<mailman.99.1452688353.13488.python-list@python.org>
In reply to#101605
On Wed, Jan 13, 2016 at 11:23 PM, Alan Robinson
<arobinson@lordlawson.org.uk> wrote:
> def menu():
>     option = int(input("Please select an option: \n 1: Set Generation 0 Values \n 2: View Generation 0 Values \n 3: Run Model \n 4: Print values"))
>
>     if option == 1:
>         juveniles,adults,seniles = setGen()
>     elif option == 2:
>         displayGen()
>     elif option == 3:
>         runModel(juveniles,adults,seniles)
>     elif option == 4:
>         print(juveniles,adults,seniles)
>     menu()
>

This is a classic use of recursion instead of iteration. When you call
menu() again, you're creating a completely new 'slot' for the new
function; it has its own set of names. Assigning to names in one call
of menu() has no effect on any other call.

Instead, look into the way a while loop works. You'll find that your
code is simpler and clearer, plus your variables will stay set.

ChrisA

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#101608

FromAlan Robinson <arobinson@lordlawson.org.uk>
Date2016-01-13 04:54 -0800
Message-ID<5b66e2de-bc73-4200-a9c1-645d2e3f0467@googlegroups.com>
In reply to#101606
On Wednesday, 13 January 2016 12:32:51 UTC, Chris Angelico  wrote:
> On Wed, Jan 13, 2016 at 11:23 PM, Alan Robinson
> <arobinson@lordlawson.org.uk> wrote:
> > def menu():
> >     option = int(input("Please select an option: \n 1: Set Generation 0 Values \n 2: View Generation 0 Values \n 3: Run Model \n 4: Print values"))
> >
> >     if option == 1:
> >         juveniles,adults,seniles = setGen()
> >     elif option == 2:
> >         displayGen()
> >     elif option == 3:
> >         runModel(juveniles,adults,seniles)
> >     elif option == 4:
> >         print(juveniles,adults,seniles)
> >     menu()
> >
> 
> This is a classic use of recursion instead of iteration. When you call
> menu() again, you're creating a completely new 'slot' for the new
> function; it has its own set of names. Assigning to names in one call
> of menu() has no effect on any other call.
> 
> Instead, look into the way a while loop works. You'll find that your
> code is simpler and clearer, plus your variables will stay set.
> 
> ChrisA
thanks I need the menu to run again not sure how to do that though

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#101609

FromChris Angelico <rosuav@gmail.com>
Date2016-01-14 00:05 +1100
Message-ID<mailman.101.1452690317.13488.python-list@python.org>
In reply to#101608
On Wed, Jan 13, 2016 at 11:54 PM, Alan Robinson
<arobinson@lordlawson.org.uk> wrote:
> On Wednesday, 13 January 2016 12:32:51 UTC, Chris Angelico  wrote:
>> On Wed, Jan 13, 2016 at 11:23 PM, Alan Robinson
>> <arobinson@lordlawson.org.uk> wrote:
>> > def menu():
>> >     option = int(input("Please select an option: \n 1: Set Generation 0 Values \n 2: View Generation 0 Values \n 3: Run Model \n 4: Print values"))
>> >
>> >     if option == 1:
>> >         juveniles,adults,seniles = setGen()
>> >     elif option == 2:
>> >         displayGen()
>> >     elif option == 3:
>> >         runModel(juveniles,adults,seniles)
>> >     elif option == 4:
>> >         print(juveniles,adults,seniles)
>> >     menu()
>> >
>>
>> This is a classic use of recursion instead of iteration. When you call
>> menu() again, you're creating a completely new 'slot' for the new
>> function; it has its own set of names. Assigning to names in one call
>> of menu() has no effect on any other call.
>>
>> Instead, look into the way a while loop works. You'll find that your
>> code is simpler and clearer, plus your variables will stay set.
>>
>> ChrisA
> thanks I need the menu to run again not sure how to do that though

Not quite. You don't want the menu to run again; you want it to
continue to run. Look up the 'while' loop and what it does.

ChrisA

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#101610

FromPeter Otten <__peter__@web.de>
Date2016-01-13 14:05 +0100
Message-ID<mailman.102.1452690357.13488.python-list@python.org>
In reply to#101608
Alan Robinson wrote:

> On Wednesday, 13 January 2016 12:32:51 UTC, Chris Angelico  wrote:
>> On Wed, Jan 13, 2016 at 11:23 PM, Alan Robinson
>> <arobinson@lordlawson.org.uk> wrote:
>> > def menu():
>> >     option = int(input("Please select an option: \n 1: Set Generation 0
>> >     Values \n 2: View Generation 0 Values \n 3: Run Model \n 4: Print
>> >     values"))
>> >
>> >     if option == 1:
>> >         juveniles,adults,seniles = setGen()
>> >     elif option == 2:
>> >         displayGen()
>> >     elif option == 3:
>> >         runModel(juveniles,adults,seniles)
>> >     elif option == 4:
>> >         print(juveniles,adults,seniles)
>> >     menu()
>> >
>> 
>> This is a classic use of recursion instead of iteration. When you call
>> menu() again, you're creating a completely new 'slot' for the new
>> function; it has its own set of names. Assigning to names in one call
>> of menu() has no effect on any other call.
>> 
>> Instead, look into the way a while loop works. You'll find that your
>> code is simpler and clearer, plus your variables will stay set.
>> 
>> ChrisA
> thanks I need the menu to run again not sure how to do that though

def menu():
    option = 1 # make sure setGen is invoked on first iteration
    while option: # choosing 0 ends the while loop
        if option == 1:
           juveniles, adults, seniles = setGen()
        elif option == 2:
           ...
        option = int(input(...)) # choose option for the next iteration

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#101611

FromAlan Robinson <arobinson@lordlawson.org.uk>
Date2016-01-13 05:22 -0800
Message-ID<cfe57c30-6fc0-4d8d-bce3-de10116874fa@googlegroups.com>
In reply to#101610
On Wednesday, 13 January 2016 13:06:11 UTC, Peter Otten  wrote:
> Alan Robinson wrote:
> 
> > On Wednesday, 13 January 2016 12:32:51 UTC, Chris Angelico  wrote:
> >> On Wed, Jan 13, 2016 at 11:23 PM, Alan Robinson
> >> <arobinson@lordlawson.org.uk> wrote:
> >> > def menu():
> >> >     option = int(input("Please select an option: \n 1: Set Generation 0
> >> >     Values \n 2: View Generation 0 Values \n 3: Run Model \n 4: Print
> >> >     values"))
> >> >
> >> >     if option == 1:
> >> >         juveniles,adults,seniles = setGen()
> >> >     elif option == 2:
> >> >         displayGen()
> >> >     elif option == 3:
> >> >         runModel(juveniles,adults,seniles)
> >> >     elif option == 4:
> >> >         print(juveniles,adults,seniles)
> >> >     menu()
> >> >
> >> 
> >> This is a classic use of recursion instead of iteration. When you call
> >> menu() again, you're creating a completely new 'slot' for the new
> >> function; it has its own set of names. Assigning to names in one call
> >> of menu() has no effect on any other call.
> >> 
> >> Instead, look into the way a while loop works. You'll find that your
> >> code is simpler and clearer, plus your variables will stay set.
> >> 
> >> ChrisA
> > thanks I need the menu to run again not sure how to do that though
> 
> def menu():
>     option = 1 # make sure setGen is invoked on first iteration
>     while option: # choosing 0 ends the while loop
>         if option == 1:
>            juveniles, adults, seniles = setGen()
>         elif option == 2:
>            ...
>         option = int(input(...)) # choose option for the next iteration

that's really helpful I understand whats happening now I just need to work out how to do this loop as I am new it looks difficult to do here goes

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#101612

FromAlan Robinson <arobinson@lordlawson.org.uk>
Date2016-01-13 05:26 -0800
Message-ID<8c528328-0dcd-49df-8d0c-d4519f24ea3a@googlegroups.com>
In reply to#101611
On Wednesday, 13 January 2016 13:23:04 UTC, Alan Robinson  wrote:
> On Wednesday, 13 January 2016 13:06:11 UTC, Peter Otten  wrote:
> > Alan Robinson wrote:
> > 
> > > On Wednesday, 13 January 2016 12:32:51 UTC, Chris Angelico  wrote:
> > >> On Wed, Jan 13, 2016 at 11:23 PM, Alan Robinson
> > >> <arobinson@lordlawson.org.uk> wrote:
> > >> > def menu():
> > >> >     option = int(input("Please select an option: \n 1: Set Generation 0
> > >> >     Values \n 2: View Generation 0 Values \n 3: Run Model \n 4: Print
> > >> >     values"))
> > >> >
> > >> >     if option == 1:
> > >> >         juveniles,adults,seniles = setGen()
> > >> >     elif option == 2:
> > >> >         displayGen()
> > >> >     elif option == 3:
> > >> >         runModel(juveniles,adults,seniles)
> > >> >     elif option == 4:
> > >> >         print(juveniles,adults,seniles)
> > >> >     menu()
> > >> >
> > >> 
> > >> This is a classic use of recursion instead of iteration. When you call
> > >> menu() again, you're creating a completely new 'slot' for the new
> > >> function; it has its own set of names. Assigning to names in one call
> > >> of menu() has no effect on any other call.
> > >> 
> > >> Instead, look into the way a while loop works. You'll find that your
> > >> code is simpler and clearer, plus your variables will stay set.
> > >> 
> > >> ChrisA
> > > thanks I need the menu to run again not sure how to do that though
> > 
> > def menu():
> >     option = 1 # make sure setGen is invoked on first iteration
> >     while option: # choosing 0 ends the while loop
> >         if option == 1:
> >            juveniles, adults, seniles = setGen()
> >         elif option == 2:
> >            ...
> >         option = int(input(...)) # choose option for the next iteration
> 
> that's really helpful I understand what's happening now I just need to work out how to do this loop as I am new it looks difficult to do here goes not too sure what you mean by make sure setGen is invoked on the first iteration?

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