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Newsgroups: comp.lang.python
Date: Wed, 26 Dec 2012 16:19:08 -0800 (PST)
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Subject: Re: Please help if you can!
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Xref: csiph.com comp.lang.python:35560

I cannot tell you how grateful I am that you took the time to do all of thi=
s.  I have been working on it all day and you are a better teacher in a few=
 minutes than my teacher has been in 4 months.  THANK YOU!

And thank you again, Mitya.  I really appreciate your time and effort too! =
 Someday I'll be advanced enough to understand it lol

I'm going to take a break and work on it more tomorrow.  I'll be back.

Thank you!


On Wednesday, December 26, 2012 6:57:39 PM UTC-5, Joshua Landau wrote:
> THIS IS A LONG POST, BUT IF YOU WANT TO LEARN YOU SHOULD READ IT. SERIOUS=
LY.
>=20
>=20
> UNLIKE Mitya Sirenef's THIS DOES NOT ASSUME MORE KNOWLEDGE THAN IS IN YOU=
R POST ALREADY, ALTHOUGH HIS IS=A0DEFINITELY=A0BETTER OVERALL. AS SUCH, THE=
RE ARE NO FUNCTIONS.
>=20
>=20
>=20
> OK. There are several small errors in here, but there's nothing too large=
 or worth much worry.
>=20
>=20
>=20
> On 26 December 2012 21:40,=A0<bobflipp...@gmail.com>=A0wrote:
>=20
>=20
> I really hope you can help!
>=20
> I need to create a program where the user can order any combination and q=
uantity of 3 products. I then offer a 10% discount if the customer correctl=
y answers a trivia question. =A0After that, there are 3 choices for shippin=
g.
>=20
>=20
>=20
> I have most of the program completed but I'm struggling with the most imp=
ortant parts :/ =A0I get the total of multiple orders of the same item, but=
 we can't figure out how to total the entire order - before discounts and s=
hipping - and then where to put any code referring back to the trivia quest=
ion. Can somebody please help me with this? I would really appreciate it!
>=20
>=20
>=20
>=20
>=20
> You write that you "need" to do this, which may hint that this is some so=
rt of homework. If so, it's generally a nice thing to say as much. That sai=
d, as long as you've given a good shot at it it's normally fine.
>=20
>=20
> =A0This is the code:
>=20
>=20
>=20
>=20
>=20
> My *very first* thought about this code is that it's really badly spaced.=
 Don't put lines together so much! [https://gist.github.com/4383950] shows =
how much nicer things look when they're partitioned more. You may not agree=
, but it took about 10 seconds and I prefer it.
>=20
>=20
> =A0shop_again =3D 'y'
>=20
>=20
>=20
>=20
>=20
> Hold on! Hold on!
> shop_again should have a True/False value. It is screaming to be a boolea=
n. "y" is a letter, not a boolean. Thus:
>=20
>=20
> shop_again =3D True
>=20
>=20
>=20
>=20
> This is important because you don't really want to get confused with all =
your types. What if shop_again was later changed to be True when a button w=
as clicked. Why on earth would you set it to "y"? You'd set it to True. Thu=
s, the sensible option is to have your types right from the very start.
>=20
>=20
>=20
> print("Welcome to the Star Wars Shop!")
>=20
>=20
> customer =3D eval(input("Is there a customer in line? (1 =3D yes, 2 =3D n=
o)> "))
>=20
>=20
>=20
> eval(input(TEXT)) is a *bad* idea.
>=20
>=20
> First of all, eval is really dangerous. Answer "yes" instead and it'll ju=
st crash. Answer True and it'll run... BUT do *neither* the if or the elif!=
 That's *bad*.
>=20
>=20
> Secondly, you don't need it. Your:
>=20
>=20
> "if(customer =3D=3D 1)" could be "if(customer =3D=3D '1')", which would w=
ork without the eval.
>=20
>=20
> And then you've got the standard of "Y/N". So a better question would be:
>=20
>=20
>=20
>=20
> customer =3D input("Is there a customer in line? [Y/N]> ")
>=20
>=20
> Finally, you want to accept "Y" *and* "y", so you'd really want:
>=20
>=20
>=20
>=20
> customer =3D input("Is there a customer in line? [Y/N]> ").lower()
>=20
>=20
>=20
> ---------
> customer =3D input("Is there a customer in line? [Y/N]> ").lower()
>=20
>=20
>=20
> Because customer really deserves to be boolean [True/False], you'd want t=
o change it immediately.
>=20
>=20
> customer =3D (customer =3D=3D "y")
>=20
>=20
> This second line assumes that all non-"y"s are False, but that's a folly =
you'll have to live with for now.
>=20
>=20
>=20
> while shop_again =3D=3D 'y':
>=20
>=20
>=20
>=20
>=20
> If you've changed shop_again to be boolean:
>=20
>=20
> while shop_again:
> =A0
> Some people don't get how this line would make sense. But it does. The "w=
hile" statement only cares if it's value it gets is "truthy". Here are lots=
 of truthy things:
>=20
>=20
>=20
>=20
> "y" =3D=3D "y"
> True
> False =3D=3D False
> not False
> "egg loaf"
> [1, 2, 1, False, False]
>=20
>=20
> and here are some falsy things:
>=20
>=20
>=20
>=20
> "n" =3D=3D "y"
> False
> True =3D=3D False
> not True
> ""
> []
>=20
>=20
> If this makes no sense, please just say.
>=20
>=20
>=20
> =A0 =A0 if (customer =3D=3D 2):
>=20
>=20
>=20
>=20
>=20
> Again, if you've done my changes from above:
>=20
>=20
>=20
> if not customer:
> =A0
>=20
> =A0 =A0 =A0 =A0 print("Welcome to the Star Wars Memorabilia Shop!")
> =A0 =A0 =A0 =A0 customer =3D eval(input("Is there a customer in line? (1 =
=3D yes, 2 =3D no)> "))
>=20
>=20
>=20
> Again:
>=20
>=20
>=20
>=20
> customer =3D input("Is there a customer in line? [Y/N]> ").lower()
>=20
> customer =3D (customer =3D=3D "y")
>=20
> =A0
> BUT HOLD ON!
>=20
>=20
> Run your program and then answer "2" twice. What happens? It's not good.
>=20
>=20
>=20
>=20
> The problem is that answering "2" to this second one doesn't skip the loo=
p!
>=20
>=20
> x =3D ASK
> LOOP:
> =A0 =A0 if not x:
> =A0 =A0 =A0 =A0 ASK
> =A0 =A0 if x:
>=20
>=20
> =A0 =A0 =A0 =A0 STUFF
> =A0 =A0 MORE STUFF
>=20
>=20
> Where you want:
>=20
>=20
>=20
> x =3D ASK
> LOOP:
> =A0 =A0 if not x:
> =A0 =A0 =A0 =A0 ASK
> =A0 =A0 if x:
> =A0 =A0 =A0 =A0 STUFF
>=20
>=20
> =A0 =A0 =A0 =A0 MORE STUFF
>=20
>=20
> or (even better):
>=20
>=20
> while not x:
> =A0 =A0 x =3D ASK
> LOOP:
> =A0 =A0 STUFF
> =A0 =A0 MORE STUFF
>=20
>=20
> The second is what I've just decided to call the "ask-until-yes" model. B=
asically, you ask until you get a "yes", so you don't have to put the loop =
anywhere else. By the time the first loop is over, you *know* that x is Tru=
e!
>=20
>=20
>=20
> =A0 =A0 elif (customer =3D=3D 1):
>=20
>=20
>=20
>=20
>=20
>=20
> Again, if you've done my changes from above:
>=20
>=20
>=20
> elif customer:
> =A0
>=20
> =A0 =A0 =A0 =A0 print("Please select an item to update your order and any=
 other number to check out.")
> =A0 =A0 =A0 =A0 print("Yoda Figure: $10 each.")
> =A0 =A0 =A0 =A0 print("Star Wars Movie DVD: $20 each.")
>=20
>=20
> =A0 =A0 =A0 =A0 print("Death Star Lego Set: $200 each.")
> =A0 =A0 =A0 =A0 print(" 1 for Yoda Figure")
> =A0 =A0 =A0 =A0 print(" 2 for Star Wars Movie DVD")
> =A0 =A0 =A0 =A0 print(" 3 for Death Star Lego Set")
>=20
>=20
> =A0 =A0 order =3D eval(input("Order: "))
>=20
>=20
>=20
> Again:
>=20
>=20
> order =3D input("Order number: ")
> =A0
>=20
> =A0 =A0 if (order =3D=3D 1):
>=20
>=20
> If you've followed my advice:
>=20
>=20
> if order =3D=3D "1":
> =A0
>=20
> =A0 =A0 =A0 =A0 yoda =3D eval(input("How many Yoda Figures do you want? :=
 "))
>=20
> =A0 =A0 =A0 =A0 total =3D 10 * yoda
>=20
>=20
> Ooookkay. Now you're thinking: "BUT *surely* I need eval here!!(?)".
>=20
>=20
> You don't.
>=20
>=20
> yoda =3D int(input("How many Yoda Figures do you want? : "))
>=20
>=20
>=20
>=20
> This is better because there are so many problems with eval, and int also=
 means that you can only order whole numbers of yodas.
> You probably also want to call this "number_of_yodas", because you're not=
 defining what "yoda" is.
>=20
>=20
> =A0=A0 =A0 =A0 =A0 print("Total:", total)
>=20
> =A0 =A0 =A0 =A0 print("Current order:", yoda, "at", total)
>=20
> =A0 =A0 if (order =3D=3D 2):
>=20
>=20
>=20
>=20
>=20
> If you've followed my advice:
>=20
>=20
> if order =3D=3D "2":
> =A0
>=20
> =A0 =A0 =A0 =A0 movie =3D eval(input("How many Star Wars Movie DVDs do yo=
u want? : "))
>=20
> =A0 =A0 =A0 =A0 total =3D 20 * movie
>=20
>=20
> As above:
>=20
>=20
> number_of_movies =3D int(input("How many Star Wars Movie DVDs do you want=
? : "))
>=20
> total =3D 20 * number_of_movies=A0
>=20
>=20
>=20
> =A0 =A0 =A0 =A0 print("Total:", total)
>=20
> =A0 =A0 =A0 =A0 print("Current order:", movie, "at", total)
>=20
> =A0 =A0 if (order =3D=3D 3):
>=20
>=20
>=20
>=20
>=20
> If you've followed my advice:
>=20
>=20
> if order =3D=3D "3":
> =A0
>=20
> =A0 =A0 =A0 =A0 legos =3D eval(input("How many Death Star Lego Sets do yo=
u want? : "))
>=20
> =A0 =A0 =A0 =A0 total =3D 200 * legos
>=20
>=20
>=20
> As above:
>=20
>=20
> number_of_legos =3D int(input("How many Death Star Lego Sets do you want?=
 : "))
>=20
> total =3D 20 * number_of_legos
>=20
>=20
> =A0=A0 =A0 =A0 =A0 print("Total:", total)
>=20
> =A0 =A0 =A0 =A0 print("Current order:", legos, "at", total)
>=20
>=20
>=20
>=20
> =A0 =A0 shop_again =3D input("Would you like to keep shopping? 'Y' for ye=
s, 'N' for no: ")
>=20
>=20
> Again:
>=20
>=20
> shop_again =3D input("Would you like to keep shopping? [Y/N]> ").lower()
>=20
>=20
>=20
> shop_again =3D (shop_again =3D=3D "y")
> =A0
>=20
> =A0 =A0 print()print("Your order before shipping and discounts: ",total)
>=20
> print()
>=20
> print("Answer a trivia question for a discount!")
>=20
> discount =3D eval(input("On what planet did Yoda live when Luke Skywalker=
 first met him? 1) Earth 2) Dagobah 3) Pluto :"))
>=20
>=20
> Again:
>=20
>=20
> discount =3D input("On what planet did Yoda live when Luke Skywalker firs=
t met him? 1) Earth 2) Dagobah 3) Pluto :")
>=20
>=20
>=20
> if (discount =3D=3D 1):
>=20
> =A0 =A0 print("Sorry, that answer was wrong!")
>=20
> if (discount =3D=3D 2):=A0 =A0 print("That's correct, you get a 10% disco=
unt!")
>=20
> if (discount =3D=3D 3):
>=20
> =A0 =A0 print("Sorry, that answer was wrong!")=A0
>=20
>=20
> If you've taken my advice:
>=20
>=20
> =A0if discount =3D=3D "1":
> =A0 =A0 print("Sorry, that answer was wrong!")
>=20
>=20
> if discount =3D=3D "2":
> =A0 =A0 print("That's correct, you get a 10% discount!")
> if discount =3D=3D "3":
> =A0 =A0 print("Sorry, that answer was wrong!")=A0
>=20
>=20
> =A0print()
>=20
> if (discount =3D=3D 2):
>=20
>=20
> If you've taken my advice:
>=20
>=20
>=20
> if discount =3D=3D "2":
>=20
> =A0
>=20
> =A0 =A0 (total * .9)
>=20
>=20
> Hold on! What do you think this line does? What is it meant to do?
>=20
>=20
> You meant:
>=20
>=20
> total =3D total*.9
>=20
>=20
> Which for clarity should be written:
>=20
>=20
>=20
>=20
> total =3D total * 0.9
>=20
> =A0
>=20
> =A0 =A0 print("Your total before shipping: ",total)=A0
>=20
> =A0print("1) Regular Shipping: 3-4 business days, $5.00 per $50 ordered. =
2) Express Shipping: overnight, $10 per $50 ordered. 3) Super Saver Shippin=
g: 7-10 business days, free.")
>=20
> shipping =3D eval(input("Please select the shipping method you want: "))
>=20
>=20
>=20
>=20
> Again:
> shipping =3D input("Please select the shipping method you want: ")
>=20
>=20
>=20
> if (shipping =3D=3D 1):
>=20
>=20
>=20
> If you've taken my advice:
>=20
> <br...
> Show original