Re: [Tutor] Proper uses of classes
On 04/04/2013 18:01, frank ernest wrote: Sorry about the indentation guys my mail service atomatically removed it when I pasted the text (I tried to fix it by hand but it was hard to tell if I was sucessful.) I was tring to create a list object (self) and change it using the list methods and some additional ones I will define in my class. I wanted to create some varibles which I pass to most if not all of my methods. Two of my variables are to be passed to the class apon creation of the object and then they in turn are to be passed to all or most of the methods I create (a, b in this case.) If I make a, b nonlocal I get the message that they are already nonlocal. I will need for debuging purposes to print my object in random places in my class. If I did this: self.a = a What would that create (I'm thinking local variable?)? If the line is in a class method you'd create a (using Python speak) name 'a' for every instance of your class. class alist(): def __init__(self, b, a): self.mylist = list() self.mylist.append(b) self.a = a + b def appendit(self): #I need to get a in hear without passing #it in; it must come from the init method. self.mylist.append(self.a) #(I hope I've updated the code well, I can't test it from this computer.) PS: This is not the real code that I'm Emailing: I thought I'd be better off with some simpler code that produces the same errors. As I see it all you gain from the appendit method is the ability to delay adding 'a' to mylist until you've done some other processing. Is this what you're trying to achieve, if not can you give us more detail? That way we can help you code up your requirements. -- If you're using GoogleCrap™ please read this http://wiki.python.org/moin/GoogleGroupsPython. Mark Lawrence ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Proper uses of classes
On 04/04/2013 01:01 PM, frank ernest wrote: Sorry about the indentation guys my mail service atomatically removed it when I pasted the text (I tried to fix it by hand but it was hard to tell if I was sucessful.) I was tring to create a list object (self) and change it using the list methods and some additional ones I will define in my class. I wanted to create some varibles which I pass to most if not all of my methods. Two of my variables are to be passed to the class apon creation of the object and then they in turn are to be passed to all or most of the methods I create (a, b in this case.) If I make a, b nonlocal I get the message that they are already nonlocal. I will need for debuging purposes to print my object in random places in my class. If I did this: self.a = aWhat would that create (I'm thinking local variable?)? No. a is a local variable, since it was passed as an argument. self.a is an attribute of the alist instance. class alist(): def __init__(self, b, a): self.mylist = list() self.mylist.append(b) self.a = a + b def appendit(self): #I need to get a in hear without passing #it in; it must come from the init method. self.mylist.append(self.a) #(I hope I've updated the code well, I can't test it from this computer.)PS: This is not the real code that I'm Emailing: I thought I'd be better off with some simpler code that produces the same errors. Your mail service is just broken, at least for use here. This is a text forum, and your mail has an empty text body. So each of our mail readers has to try to reconstruct the text from html nonsense. You can see the result above of what Thunderbird does. The following is what I think you posted. class alist(): def __init__(self, b, a): self.mylist = list() self.mylist.append(b) self.a = a + b def appendit(self): #I need to get a in hear without passing #it in; it must come from the init method. self.mylist.append(self.a) #(I hope I've updated the code well, I can't test it from this computer.) There are lots of terminology problems which will stop you from understanding what's going on. "I wanted to create some varibles which I pass to most if not all of my methods" "Variables" passed to methods are called arguments, or parameters, and that's NOT what you're trying to do. You're trying to have the __init__() method "remember" those values. When you write "self.a =" you are creating an "instance attribute" which is visible to all methods on that instance. Other methods can access that instance attribute by referring to it as self.a Not by "global" not by "nonlocal". Those are very different. A local variable is also different, as is a class attribute. You need to study up on each of these terms, and see what the differences are in terms of lifetime, visibility, duplication, etc. More on that later. Now, the appendit() method is nonsensical, but perhaps it was just a sample. Each time it's called, it'll append the same value a to the list. Perhaps you'd be more comfortable if you wrote a __str__() method. That way, when you try to print an instance, it'll do what you say, rather than some default. Typically, it should do something with each attribute that was initialized by __init__(). (untested) def __str__(self): res = "mylist attribute is" + str(self.mylist) + "\n" res += "a is " + str(a) + "\n" return res Now you can exercise your class, and print out the results as often as you like: (untested) obj1 = alist(3, 47) # creates an instance of alist print(obj1) # prints it obj2 = alist(12, 9) # creates a second instance of alist, with its own self.mylist and self.a, different from those in obj1 print(obj2) obj1.append() #will take the particular list in obj1, and append the saved self.a value print(obj1) obj2.append() obj2.append() print(obj) Now, a brief, informal summary of all the different kinds of "variables." A global variable is defined at the outer scope of a module, and should mostly be constants, for sound engineering reasons. The global keyword, used only inside a function, declares that a particular variable that looks like it ought to be local, in fact is global. The keyword applies only to that particular function. A local variable is defined and used within a function (or method), and vanishes entirely when the function returns. The formal parameters of the function are locals as well. A class attribute belongs to the class, and there's only one of them, regardless of how many instances that class has. An instance attribute exists separately in each instance of a class. It should (my preference) be initialized in the __init__() method so that every instance has the same attributes, even if it's just self.att = None A nonlocal variable is probably beyond what you need to know at the present, but it's one that's either glo
[Tutor] Socket Programming
I want to perform bind function for socket programming between two
computers of ip addresses- 172.18.2.11 and 172.18.2.95 using the following
command(on the computer having IP address 172.18.2.95):
s=socket.socket(socket.AF_INIT,socket.SCK_DGRM))
s.bind(('172.18.2.11',8032))
But error is occurring showing "bind not done"
The ping operation of command prompt is showing that the computers are
connected.
Please help me.
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[Tutor] basic question
Hi,
My name is Najam, I am very new to Python Programming. Would you please help me
with the following question?
The question/problem is,
Write a Car salesman program where the user enters the base price of a car. The
program should add a bunch of extra fees such as tax, license, dealer prep, and
destination charge.Make tax and license a percent of the base price. The other
fees should be set values. Display the actual price of the car once all the
extras are applied.
I am not sure whether I have entered the right code for "Make tax and license a
percent of the base price." or not.
My program is;
price = float(raw_input("Enter the base price of the car $ "))
tax = float(raw_input("Enter the tax $ "))
licence = float(raw_input("Enter the licence fees $ "))
dealer_prep = float(raw_input("Enter the dealer prep fees $ "))
des_charge = float(raw_input("Enter the destination charge $ "))
percent = (tax * 0.01 + licence * 0.01) / price
# ?
print "\nA percent of the base price is: $ " , percent
total = price + tax + licence + dealer_prep + des_charge
print "\nThe actual price of the car is: $ " , total
raw_input("\nPress Enter key to Exit, thank you.")
Thank you.
Najam.
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Re: [Tutor] basic question
On 04/05/2013 08:05 AM, Najam Us Saqib wrote:
Hi,
My name is Najam, I am very new to Python Programming.
Welcome.
Would you please help me with the following question?
The question/problem is,
Write a Car salesman program where the user enters the base price of a car. The
program should add a bunch of extra fees such as tax, license, dealer prep, and
destination charge.Make tax and license a percent of the base price. The other
fees should be set values. Display the actual price of the car once all the
extras are applied.
Is this exactly the way the assignment reads, or did you paraphrase it?
I am not sure whether I have entered the right code for "Make tax and license a
percent of the base price." or not.
My program is;
price = float(raw_input("Enter the base price of the car $ "))
tax = float(raw_input("Enter the tax $ "))
licence = float(raw_input("Enter the licence fees $ "))
dealer_prep = float(raw_input("Enter the dealer prep fees $ "))
des_charge = float(raw_input("Enter the destination charge $ "))
percent = (tax * 0.01 + licence * 0.01) / price
# ?
print "\nA percent of the base price is: $ " , percent
total = price + tax + licence + dealer_prep + des_charge
print "\nThe actual price of the car is: $ " , total
raw_input("\nPress Enter key to Exit, thank you.")
The way I expect the assignment was intended is that the user should
enter (with raw_input) the tax and license as percentages, and you
convert them to dollars, rather than the other way around.
--
DaveA
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Re: [Tutor] basic question
On 4/5/13, Woody 544 wrote:
> Dear Najam
>
> The tax and license amounts should not need to be entered, as I would
> think the only variable is the base price, with tax and license
> calculated as their rate times the base price. For example, if the
> sales tax rate for the area is 6% for example:
>
> tax = price * 0.06
>
> Since the other fees are fixed, there is no need for raw input from
> the user on those either and the rates can be hard coded in. If the
> tax rate = 6% and the license rate = 1% then:
>
> total = price + (price*.06) + (price * .01) + dealer_prep + des_charge
>
> Thus the only input from the user would be to enter the base price.
> Of course, if the intent is for more than just one dealership with
> varied rates and fees, it may make sense for the other values to be
> entered by a user.
>
> MJ
>
> On 4/5/13, Najam Us Saqib wrote:
>> Hi,
>>
>> My name is Najam, I am very new to Python Programming. Would you please
>> help
>> me with the following question?
>>
>> The question/problem is,
>>
>> Write a Car salesman program where the user enters the base price of a
>> car.
>> The program should add a bunch of extra fees such as tax, license, dealer
>> prep, and destination charge.Make tax and license a percent of the base
>> price. The other fees should be set values. Display the actual price of
>> the
>> car once all the extras are applied.
>>
>> I am not sure whether I have entered the right code for "Make tax and
>> license a percent of the base price." or not.
>>
>> My program is;
>>
>> price = float(raw_input("Enter the base price of the car $ "))
>>
>> tax = float(raw_input("Enter the tax $ "))
>> licence = float(raw_input("Enter the licence fees $ "))
>> dealer_prep = float(raw_input("Enter the dealer prep fees $ "))
>> des_charge = float(raw_input("Enter the destination charge $ "))
>>
>> percent = (tax * 0.01 + licence * 0.01) / price
>> # ?
>>
>> print "\nA percent of the base price is: $ " , percent
>>
>> total = price + tax + licence + dealer_prep + des_charge
>>
>> print "\nThe actual price of the car is: $ " , total
>>
>> raw_input("\nPress Enter key to Exit, thank you.")
>>
>>
>>
>> Thank you.
>> Najam.
>>
>
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Re: [Tutor] Socket Programming
On 05/04/13 21:47, Mousumi Basu wrote:
I want to perform bind function for socket programming between two
computers of ip addresses- 172.18.2.11 and 172.18.2.95 using the following
command(on the computer having IP address 172.18.2.95):
s=socket.socket(socket.AF_INIT,socket.SCK_DGRM))
I get THREE errors with that line:
* SyntaxError due to an extra closing parenthesis;
* after fixing that problem, I get an AttributeError:
'module' object has no attribute 'AF_INIT'
* after guessing what you mean instead of AF_INIT, I get another AttributeError:
'module' object has no attribute 'SCK_DGRM'
Could you show us the code you are actually using, and save us from having to
guess?
s.bind(('172.18.2.11',8032))
But error is occurring showing "bind not done"
Please copy and paste the complete traceback, starting with the line:
Traceback (most recent call last)
and going all the way to the end of the error message.
--
Steven
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Re: [Tutor] Socket Programming
Have you checked out the socket HOWTO?
http://docs.python.org/2/howto/sockets.html
Cheers
On Friday, April 05, 2013, Mousumi Basu wrote:
> I want to perform bind function for socket programming between two
> computers of ip addresses- 172.18.2.11 and 172.18.2.95 using the following
> command(on the computer having IP address 172.18.2.95):
>
> s=socket.socket(socket.AF_INIT,socket.SCK_DGRM))
> s.bind(('172.18.2.11',8032))
>
> But error is occurring showing "bind not done"
>
> The ping operation of command prompt is showing that the computers are
> connected.
>
> Please help me.
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Re: [Tutor] TypeError: can't multiply sequence by non-int of type 'float'
Thanks all...I realized my mistake!!...:) On 4 April 2013 20:12, Andreas Perstinger wrote: > Sayan Chatterjee wrote: > > >I know this error occurs when one tries to multiply a string with a > >fraction i.e float. In my case , I can't figure out how can a numpy > >floating point array be a string. > > The problem is not that the numpy array is a string but that you append > the array to a python list: > > > pv_za=[] > > pv_za.append(-K*np.sin(K*pv_za_temp)) > > pv_za_temp = [] > > pv_za_temp.append(np.array(pv_za)) > > Both "pv_za" and "pv_za_temp" are python lists to which you append a > numpy array. But since you delete both lists in each iteration I assume > you want to just assign a new numpy array to both names: > > pv_za = -K * np.sin(K * pv_za_temp) > pv_za_temp = pv_za # "pv_za" is already a numpy array > > Bye, Andreas > ___ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > -- -- *Sayan Chatterjee* Dept. of Physics and Meteorology IIT Kharagpur Lal Bahadur Shastry Hall of Residence Room AB 205 Mob: +91 9874513565 blog: www.blissprofound.blogspot.com Volunteer , Padakshep www.padakshep.org ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
