[Tutor] trouble with "if"
adamurbas at hotmail.com
Sun May 27 19:49:04 CEST 2007
Thank you for the help Brian. I would like to ask you about these things. Which one of the examples you gave would be most fool proof.> Date: Wed, 23 May 2007 13:40:09 -0400> From: broek at cc.umanitoba.ca> To: adamurbas at hotmail.com> CC: tutor at python.org> Subject: Re: [Tutor] trouble with "if"> > adam urbas said unto the world upon 05/23/2007 01:04 PM:> > Sorry, I don't think Hotmail has turn off HTML. If it does I> > havn't been able to find it. I think you're going to have to> > explain your little bit of text stuff down there at the bottom. I> > have no idea what most of that means. All my choice things are> > working now though. I think that is what you were trying to help> > me with. What I used wasif shape in["1","circle"]:and if shape ==> > "1" or shape =="circle":It works perfectly fine now.Ya that little> > bit o' code is really puzzling. I wish I knew more about this> > python deal. I understand the concept, but not the rules or the> > techniques and things of that sort. OK... I've got it... the> > data=raw_input('Feed Me!'). Ok I now understand that bit. Then it> > says Feed Me! and you put 42 (the ultimate answer to life the> > universe, everything). OK, it won't accept the <type 'str'> bit.> > it doesn't like the "<". Well, I just removed that bit and it> > said:Feed Me! and I put 42, and it said >>> (I guess it's> > satisfied now, with the whole feeding). Well if I understood what> > 'str' meant, then I could probably figure the rest out. Well I> > have to go do other things so I'll save the rest of this figuring> > out till later.I shall return,Adam> Date: Wed, 23 May 2007 12:12:16> > -0400> From: broek at cc.umanitoba.ca> To: adamurbas at hotmail.com> CC:> > tutor at python.org> Subject: Re: [Tutor] trouble with "if"> > adam> > urbas said unto the world upon 05/23/2007 11:57 AM:> > > > Hi all,>> > > > > I've been working with this new program that I wrote. I> > started out > > with it on a Ti-83, which is much easier to program> > than python. Now > > I'm trying to transfer the program to python> > but its proving to be quite > > difficult. I'm not sure what the> > whole indentation thing is for. And > > now I'm having trouble> > with the if statement things. > > > > #"Circle Data Calculation> > Program:"> > print "Welcome to the Circle Data Calcuation> > Program."> > print> > > > #"Menu 1:"> > print "Pick a shape:">> > > print "(NOTE: You must select the number of the shape and not the> > shape > > itself)"> > print "1 Circle"> > print "2 Square"> > print> > "3 Triangle"> > > > #"User's Choice:"> > shape=raw_input("> ")>> > > > > #"Select Given:"> > if shape == 1:> > print> > "Choose the given value:"> > print "1 radius"> >> > print "2 diameter"> > print "3 circumference"> >> > print "4 area"> > > > #"User's Choice:"> > given=raw_input("> ")> >> > > > if given == 1:> > radius=raw_input("Enter Radius:")> >> > diameter=(radius*2)> > circumference=(diameter*3.14)> >> > area=(radius**2*3.14)> > print "Diameter:", diameter> >> > print "Circumference:", circumference> > print "Area:",> > area> > > > if given == 2:> > diameter=raw_input("Enter> > Diameter:")> > radius=(diameter/2)> >> > circumference=(diameter*3.14)> > area=(radius**2*3.14)> >> > print "Radius:", radius> > print "Circumference:",> > circumference> > print "Area:", area> > > > if given == 3:>> > > circumference=raw_input("Enter Circumference:")> >> > radius=(circumference/3.14/2)> > diameter=(radius*2)> >> > area=(radius**2*3.14)> > print "Radius:", radius> >> > print "Diameter:", diameter> > print "Area:", area> > > >> > if given == 4:> > area=raw_input("Enter Area:")> >> > radius=(area/3.14)> > > > This is the whole program so> > far, because I haven't quite finished it > > yet. But I tried to> > get it to display another list of options after you > > select a> > shape but it just does this.> > > > Pick a shape:> > 1 Circle> > 2> > Square> > 3 Triangle> > >1> > >1> > >>>> > > > I'm not sure why> > it does that but I do know that it is skipping the > > second list> > of options.> > > > Another of my problems is that I can't figure> > out how to get it to > > accept two different inputs for a> > selection. Like I want it to accept > > both the number 1 and> > circle as circle then list the options for > > circle. It won't> > even accept words. I can only get it to accept > > numbers. It's> > quite frustrating actually.> > > > Any advice would be greatly> > appreciated.> > Thanks in advance,> > Adam> > > > > > > Adam,> >> > Could you send plain text email rather than html, please? At least> > for > me, your code's indentation is all messed up unless I take> > some steps > to rectify it.> > The problem is that raw_input> > returns a string, and you are testing > whether given is equal to> > integers. See if this helps make things clear:> > >>> data => > raw_input('Feed me!')> Feed me!42> >>> type(data)> <type 'str'>>> > >>> data == 42> False> >>> int(data) == 42> True> >>>> > Best,> >> > Brian vdB > > > Adam,> > As you can see from the above, the way hotmail is formatting things > makes the conversation a bit tricky :-) I'm only willing to spend so > much time trying to sort through it, so I hope what follows helps.> > >>> data = raw_input("Feed me!")> Feed me!42> > This calls the builtin function raw_input with a parameter setting the > prompt to "Feed me!" and assigns the result to data. Since I hit 42 > and then enter,> > >>> data> '42'> > Notice the quotes around 42. They indicate that the value of data is a > string. That's what this tells us:> > >>> type(data)> <type 'str'>> > The string '42' is not the same as the integer 42:> > >>> type(42)> <type 'int'>> >>> '42' == 42> False> > So, when you had an if test that was something like:> > if given == 1:> # Do stuff here> > the equality comparison was never going to work---given was a string > returned by raw_input and no string is ever equal to an integer.> > What I suggested was taking the string returned by raw_input and > feeding it to int() to transform it from a string to an integer, and > allow your if test to stand a chance:> > >>> data = raw_input("Feed me!")> Feed me!42> >>> if data == 42:> ... print "Matches!"> ...> >>> data = int(raw_input("Feed me!"))> Feed me!42> >>> if data == 42:> ... print "Matches!"> ...> Matches!> >>>> > There are other ways, for instance:> > >>> data = raw_input("Feed me!")> Feed me!42> >>> if data == '42':> ... print "Matches!"> ...> Matches!> >>>> > Here, instead of transforming data to an int and then testing for > equality with 42, I left data as a string and tested for equality with > the string '42'.> > The way calling int() is a bit better, I think. If the user enters a > few spaces, then 42 then a few more spaces, that way will still work:> > >>> data = int(raw_input("Feed me!"))> Feed me! 42> >>> if data == 42:> ... print "Matches!"> ...> Matches!> >>>> > because> > >>> int(' 42 ')> 42> >>>> > whereas> > >>> ' 42 ' == '42'> False> > > I hope there is some help in there somewhere :-)> > Brian vdB
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