[Tutor] how do (or do I) do a list of variable names?
Hello Everyone, I think my approach is all wrong, but here goes. var1 = []; var2 = []; var3 = []; . . . ~50 lists each variable would be a list of two digit integers, or two digit integers stored as strings (I don't need to do any math, I just need to know which integers are in which variable) container = [var1,var2,var3 . . . ] I'd like to be able to iterate over container or pick out one or more of my lists to write out an input (text) file for an external program. The thing is, assigning all those lists to a list gives me a list of lists, not a list of my variable names. Worse, I may or may not be able to have changes to a list show up in my list of lists, depending on how & when I do it. Really kludgy, but it is a one off that will likely never be used again. TIA, Rick signature.asc Description: OpenPGP digital signature ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] how do (or do I) do a list of variable names?
rick wrote:
> Hello Everyone,
>
> I think my approach is all wrong, but here goes.
>
> var1 = []; var2 = []; var3 = []; . . . ~50 lists
>
>
> each variable would be a list of two digit integers, or two digit
> integers stored as strings (I don't need to do any math, I just need to
> know which integers are in which variable)
>
> container = [var1,var2,var3 . . . ]
>
> I'd like to be able to iterate over container or pick out one or more of
> my lists to write out an input (text) file for an external program.
>
> The thing is, assigning all those lists to a list gives me a list of
> lists, not a list of my variable names. Worse, I may or may not be able
> to have changes to a list show up in my list of lists, depending on how
> & when I do it.
>
> Really kludgy, but it is a one off that will likely never be used again.
You typically don't make 50 variables in Python, you use a dict:
>>> container = {
... "foo": [10, 20],
... "bar": [30, 40],
... "baz": [40, 50],
... #...
... }
you can then look up the "foo" list with
>>> print(container["foo"])
[10, 20]
If you want to know all the keys that 40 is associated with you can either
iterate through the items every time
>>> print([k for k, v in container.items() if 40 in v])
['bar', 'baz']
or build the reverse dict once
>>> for k, values in container.items():
... for v in values:
... value_to_key.setdefault(v, set()).add(k)
...
and then profit from fast lookup
>>> print(value_to_key[40])
{'bar', 'baz'}
>>> print(value_to_key[10])
{'foo'}
until you make changes to the original `container` dict.
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[Tutor] most useful ide
Hi Are there any recommendations for python ide's currently I am using idle, which seems pretty decent but am open to any suggestions cheers ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
[Tutor] sorting and writing to data file
Hello community,
Newbie here. I have a data (.dat) file with integers (2,9,1,5,7,3,9) in
it just as shown.
My instructions are to sort the numbers and rewrite them back to the
data file.
*here is my code:**
*
lab3int=[2,9,1,5,7,3,9]
lab3int.sort()
print(lab3int)
lab3int=open('lab3int.dat','w')
lab3int.write()
lab3int.close()
*here is my error message:*
[1, 2, 3, 5, 7, 9, 9]
Traceback (most recent call last):
File "lab3int.py", line 5, in
lab3int.write()
TypeError: function takes exactly 1 argument (0 given)
I know that it is telling me that my error is in line #5. If I put
anything in the () for lab3int.write function, then that appears in my
data file. however, I am looking to just put the re-sorted integers
back into the data file without having to manually type each integer
manually. Is there something that i can put into the lab3int.write() to
make that happen?
Hope my problem is clear, Thanks people
ATS
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Re: [Tutor] Best version for novice
On 02/01/2014 03:35 PM, Alan Gauld wrote: On 01/02/14 18:41, Ian D wrote: Is it better to use python 3 as a newcomer who isn't really going to be writing any software as such just using it for learning? The more important question is which version does your preferred tutorial use? And are you targeting a specific platform or just for yourself? Some platforms, like Red Hat/CentOS, are still 2.x. The most current RHEL is 2.6 and the upcoming RHEL 7 is still Python 2.7. If you're doing this for yourself, or for a start-up that can use newer versions, use 3.x if your tutorial supports it. You might note in Alan's signature is a like to his site, which happens to have a nice tutorial. :) http://www.alan-g.me.uk/ Leam -- http://31challenge.net http://31challenge.net/insight ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
[Tutor] strange errors
Hi, sometimes when I try to run a program in Python I obtain some errors. The strange thing is that sometimes when I run it a second time or when I turn off the pc and I restart later to try to make it works it gives different errors. How could I avoid this problem? I think that it is because it "remember" some variables that I have used... Thanks Gabriele ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] help me
thank you so much because I got it :) On Saturday, February 1, 2014 1:28 PM, Danny Yoo wrote: On Fri, Jan 31, 2014 at 8:55 PM, hind fathallah wrote: > hi can you answer this question for me plz [question omitted] Many of us probably could answer this. But this is not a homework-answering mailing list. The problem itself is not interesting to us. What is interesting is why the problem is giving you trouble. We'd rather focus on where you are having difficulty: we'd rather help *you*. Tell us what you've tried, where you're getting stuck, what other kinds of problems you've done that are similar to this one. That is, show us what general problem solving strategies you're using now. Maybe some of those strategies are not working for you.___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] sorting and writing to data file
On 02/02/14 03:08, adrian wrote:
Newbie here. I have a data (.dat) file with integers (2,9,1,5,7,3,9) in
it just as shown.
In your code below you use a hard coded list not a data file?
lab3int=[2,9,1,5,7,3,9]
lab3int.sort()
print(lab3int)
So far so good.
lab3int=open('lab3int.dat','w')
But now you've reassigned lab3int to the file object
so you threw away all your data. You need a separate
variable to store the file pointer.
Lets call it intFile...
lab3int.write()
Would now become
intfile.write()
But your data is a sorted list of integers so you need
to convert that to a string before you can write it
to a text file.
You need a loop such as
for item in lab3int:
intFile.write( str(item) )
If you had a lot of data you might want to think
about adding some newlines when you write too...
hth
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.flickr.com/photos/alangauldphotos
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Re: [Tutor] strange errors
On 02/02/14 02:11, Gabriele Brambilla wrote: sometimes when I try to run a program in Python I obtain some errors. How are you running the program? doubly clicking in a file manager/explorer? Running from an OS command line? Importing from the Python >>> prompt? Or using some kind of IDE? (Which?) The answer to your question depends a lot on the way you run the code. A sample error and your OS and Python version will help too. How could I avoid this problem? I think that it is because it "remember" some variables that I have used... Could be. If you import a module then change that module then reimporting alone is not enough. But if you run the code from the OS that shouldn't be an issue. So how do you run the code? -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] sorting and writing to data file
Alan Gauld wrote:
> You need a loop such as
>
> for item in lab3int:
>intFile.write( str(item) )
You also need to separate the values, with a space, a newline or whatever.
So:
for item in lab3int:
intFile.write(str(item))
intFile.write("\n")
This can be simplified to
for item in lab3int:
print(item, file=intFile)
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Re: [Tutor] most useful ide
On 02/02/14 08:25, Ian D wrote: Are there any recommendations for python ide's Lots depending who you ask... currently I am using idle, which seems pretty decent but am open to any suggestions If it works for you then use it. The thing about IDEs is that they ae very personal. Some people swear by emacs, others swear at it. Some love Netbeans, or Eclipse, others hate them both. If you are a Mac user you may prefer XCode... There are lots of specialized Pyhon IDS too. And many Linux users prefer to let Linux be their IDE and just run multiple Windows to do the same job. (I'm in this camp FWIW...) A lot will also depend on whether you have used IDEs in the past, since that might sway your preferences. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] most useful ide
On Sun, Feb 2, 2014 at 1:55 PM, Ian D wrote: > Hi > > Are there any recommendations for python ide's > > currently I am using idle, which seems pretty decent but am open to any > suggestions > cheers > While not an IDE in the usual sense I have found IPython a great addition to my toolkit. YMMV Asokan Pichai ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] most useful ide
Hi Are there any recommendations for python ide's currently I am using idle, which seems pretty decent but am open to any suggestions cheers I personally prefer the Linux interpreter. Since you're asking. Scott On Sun, Feb 2, 2014 at 10:43 AM, Asokan Pichai wrote: > > > > On Sun, Feb 2, 2014 at 1:55 PM, Ian D wrote: > >> Hi >> >> Are there any recommendations for python ide's >> > >> currently I am using idle, which seems pretty decent but am open to any >> suggestions >> cheers >> > > While not an IDE in the usual sense I have found IPython a great addition > to my toolkit. > YMMV > > Asokan Pichai > > ___ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > https://mail.python.org/mailman/listinfo/tutor > > ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] strange errors
forwarding to list... Please use reply-all when responding to the list. Alan Gauld Author of the Learn To Program website http://www.alan-g.me.uk/ http://www.flickr.com/photos/alangauldphotos > > From: Gabriele Brambilla >To: Alan Gauld >Sent: Sunday, 2 February 2014, 17:31 >Subject: Re: [Tutor] strange errors > > > >I use windows 7 command prompt. doing > > >python .py > > >the errors are various...when I will get them again I will write them! > > >thanks > > >Gabriele > > > >2014-02-02 Alan Gauld : > >On 02/02/14 02:11, Gabriele Brambilla wrote: >> >> >>sometimes when I try to run a program in Python I obtain some errors. >>> >> How are you running the program? >> >>doubly clicking in a file manager/explorer? >>Running from an OS command line? >>Importing from the Python >>> prompt? >>Or using some kind of IDE? (Which?) >> >>The answer to your question depends a lot on the way you >>run the code. >> >>A sample error and your OS and Python version will help too. >> >> >> >>How could I avoid this problem? I think that it is because it "remember" >>>some variables that I have used... >>> >> Could be. If you import a module then change that module then >>reimporting alone is not enough. But if you run the code from the OS that >>shouldn't be an issue. So how do you run the code? >> >>-- >>Alan G >>Author of the Learn to Program web site >>http://www.alan-g.me.uk/ >>http://www.flickr.com/photos/alangauldphotos >> >>___ >>Tutor maillist - Tutor@python.org >>To unsubscribe or change subscription options: >>https://mail.python.org/mailman/listinfo/tutor >> > > >___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] most useful ide
>Subject: Re: [Tutor] most useful ide > >On 02/02/14 08:25, Ian D wrote: > >> Are there any recommendations for python ide's > >Lots depending who you ask... If you ask me: Spyder (free) or PyCharm (free for open source projects) ;-) ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] most useful ide
Pycharm is nice for bigger projects (since tou can collapse any section); but it's crazy resource intensive. For Linux Gedit can be made very nice for python, and of course vim in the shell is very nice with the right ~/.vimrc. On Feb 2, 2014 11:20 AM, "scurvy scott" wrote: > Hi > > Are there any recommendations for python ide's > > currently I am using idle, which seems pretty decent but am open to any > suggestions > > > cheers > > > I personally prefer the Linux interpreter. Since you're asking. > Scott > > > On Sun, Feb 2, 2014 at 10:43 AM, Asokan Pichai > wrote: > >> >> >> >> On Sun, Feb 2, 2014 at 1:55 PM, Ian D wrote: >> >>> Hi >>> >>> Are there any recommendations for python ide's >>> >> >>> currently I am using idle, which seems pretty decent but am open to any >>> suggestions >>> cheers >>> >> >> While not an IDE in the usual sense I have found IPython a great addition >> to my toolkit. >> YMMV >> >> Asokan Pichai >> >> ___ >> Tutor maillist - Tutor@python.org >> To unsubscribe or change subscription options: >> https://mail.python.org/mailman/listinfo/tutor >> >> > > ___ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > https://mail.python.org/mailman/listinfo/tutor > > ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] most useful ide
On 14-02-02 01:16 PM, Kodiak Firesmith wrote: > Pycharm is nice for bigger projects (since tou can collapse any section); > but it's crazy resource intensive. For Linux Gedit can be made very nice I prefer Geany as it will run my code with a click of the mouse. > for python, and of course vim in the shell is very nice with the right > ~/.vimrc. > On Feb 2, 2014 11:20 AM, "scurvy scott" wrote: > >> Hi >> >> Are there any recommendations for python ide's ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] most useful ide
On Feb 2, 2014 8:17 PM, "Pierre Dagenais" wrote: > > > > On 14-02-02 01:16 PM, Kodiak Firesmith wrote: > > Pycharm is nice for bigger projects (since tou can collapse any section); > > but it's crazy resource intensive. For Linux Gedit can be made very nice > > I prefer Geany as it will run my code with a click of the mouse. I prefer vim so that I never have to use the mouse. :) Oscar ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Best version for novice
On 14-02-01 08:20 PM, Steven D'Aprano wrote: > On Sat, Feb 01, 2014 at 06:41:10PM +, Ian D wrote: >> Hi >> >> Is it better to use python 3 as a newcomer who isn't really going to >> be writing any software as such just using it for learning? > > Yes, you should use Python 3, with one proviso: many tutorials, > especially the older ones, are based on Python 2. That means that you Steven is not a newbie, but I am. I suppose that makes me the expert on tutorials, LOL. I find that most useful tut are now for Python 3, when you find a Python 2 tutorial you need to convert the print statement, the tkinter import statement, and ignore any references to cPickle. In my experience everything else works as posted. PierreD. > either need to find another tutorial, or mentally adjust from Python 2 > to 3 when you read it. That's easy for an experienced user, but perhaps > not for a beginner. > > The differences aren't really that great, no more different than between > (say) British English and American English, but it may be disconcerting > for somebody who isn't confident with the language. > > Python 3 is the future of Python. All improvements are going into 3, 2 > is only getting bug fixes. If you aren't *required* to stick with Python > 2 for some reason, you should use 3. > > >> Also in 2.7 I use no subprocess by giving my python exe a -n argument, >> otherwise my canvas program's freeze. > > I'm afraid that I have no idea what you are talking about here, Python > doesn't accept a -n argument: > > [steve@ando ~]$ python2.7 -n > Unknown option: -n > usage: python2.7 [option] ... [-c cmd | -m mod | file | -] [arg] ... > Try `python -h' for more information. > > > > Regards, > > > ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] most useful ide
On 02/02/2014 03:10 PM, Pierre Dagenais wrote: On 14-02-02 01:16 PM, Kodiak Firesmith wrote: Pycharm is nice for bigger projects (since tou can collapse any section); but it's crazy resource intensive. For Linux Gedit can be made very nice I prefer Geany as it will run my code with a click of the mouse. for python, and of course vim in the shell is very nice with the right ~/.vimrc. On Feb 2, 2014 11:20 AM, "scurvy scott" wrote: Hi Are there any recommendations for python ide's I, too, use Geany to run my Python programs. Ken ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] most useful ide
W dniu 2014-02-02 18:56, Albert-Jan Roskam pisze: >> On 02/02/14 08:25, Ian D wrote: >> >>> Are there any recommendations for python ide's >> >> Lots depending who you ask... > > If you ask me: Spyder (free) or PyCharm (free for open source projects) ;-) There is also PyCharm Community Edition. Free for all projects. And if you'd ask me, it would be my answer. :) -- Best regards, Wiktor Matuszewski ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
[Tutor] Traversing lists or getting the element you want.
I am new to Python, and I do not know how to traverse lists like I
traverse arrays in C. This is my first program other than "Hello World".
I have a Raspberry Pi and they say Python is the language of choice for
that little machine. So I am going to try to learn it.
I have data in the form of x, y pairs where y = f(x) and is non linear.
It comes from a .csv file.
In this case x is an integer from 165 to 660 so I have 495 data sets.
I need to find the optimal locations of three values of x to piecewise
linear estimate the function.
So I need to find i, j, k so 165 < i < j < k < 660 and the 4 line
segments [(165, f(165)), (i, f(i))], [(i, f(i)), (j, f(j))], [(j, f(j),
(k, f(k))], [(k, f(k)), (660, f(660))].
The value I need to minimize is the square of the difference between the
line estimate and the real value at each of the 495 points.
I can do this in C. To keep it simple to understand I will assume the
arrays x[] and y[] and minsum, mini, minj, and mink are global.
I have not tested this but this is what I came up with in C. Assuming
x[] and y[] are already filled with the right values.
int x[495];
double y[495];
max_elements = 495;
double minsum;
int mini, minj, mink
void minimize(int max_elements)
{
minsum = 9.0; // big big number
for (i=2; ihttps://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Traversing lists or getting the element you want.
On Sun, Feb 2, 2014 at 3:46 PM, Kipton Moravec wrote:
> I am new to Python, and I do not know how to traverse lists like I
> traverse arrays in C. This is my first program other than "Hello World".
> I have a Raspberry Pi and they say Python is the language of choice for
> that little machine. So I am going to try to learn it.
>
>
> I have data in the form of x, y pairs where y = f(x) and is non linear.
> It comes from a .csv file.
>
> In this case x is an integer from 165 to 660 so I have 495 data sets.
>
> I need to find the optimal locations of three values of x to piecewise
> linear estimate the function.
>
>
> So I need to find i, j, k so 165 < i < j < k < 660 and the 4 line
> segments [(165, f(165)), (i, f(i))], [(i, f(i)), (j, f(j))], [(j, f(j),
> (k, f(k))], [(k, f(k)), (660, f(660))].
>
> So as you iterate through the minimize function below, you want something
like this, I believe:
if (165 < i) and (i < j) and (j < k) and (k < 660):
print 'true'
else:
print 'false'
> The value I need to minimize is the square of the difference between the
> line estimate and the real value at each of the 495 points.
>
>
> I can do this in C. To keep it simple to understand I will assume the
> arrays x[] and y[] and minsum, mini, minj, and mink are global.
>
>
> I have not tested this but this is what I came up with in C. Assuming
> x[] and y[] are already filled with the right values.
>
>
> int x[495];
> double y[495];
> max_elements = 495;
> double minsum;
> int mini, minj, mink
>
> #We define some vars before utilizing them x,and y are list comprehension
# You said int for x, so it's created in ints, and y is in floats
x = [num for num in range(0,496)]
# You said double for y, so the it's created in floats, and x is an int list
y = [float(num) for num in range(0,496)]
i = 0
j = 0
k = 0
max_elements = 495
mini = 0
minj = 0
mink = 0
> void minimize(int max_elements)
>
>
def minimize(max_elements):
{
> minsum = 9.0; // big big number
>
>
minsum = float(9.0) # used float just to show as double
> for (i=2; i for (j=i+2; j< max_elements -4; j++)
> for (k=j+2; k< max_elements-2;k++)
>
for i in range(2,max_elements-6):
print i
for j in range(i+2,max_elements-4):
print j
for k in range(j+2,max_elements-2):
print k
> {
> sum = error(0,i);
> sum += error(i,j);
> sum += error(j,k);
> sum += error(k,495)
>
>
sum = error(0,i)
sum += error(i,j)
sum += error(j,k)
sum += error(k,495)
> if (sum < minsum)
> {
> minsum = sum;
> mini = i;
> minj = j;
> mink = k;
> }
> }
> }
>
>
if sum < minsum:
minsum = sum
mini = i
minj = j
mink = k
>
> double error(int istart, int iend)
> {
>
>
error(int istart, int iend):
> // linear interpolation I can optimize but left
> // it not optimized for clarity of the function
>
> int m;
>
> double lin_estimate;
>
> double errorsq;
>
> errorsq = 0;
>
>
int m
lin_estimate =
errorsq = float(0) #just to show double = float type again
errorsq = 0
> for (m=istart; m {
> lin_estimate = y[istart] + ((y[iend] - y[istart]) *
>((x[m] - x[istart]) / (x[iend] - x[istart])));
>
> errorsq += (lin_estimate - y[m]) * (lin_estimate - y[m]);
> }
>
> return (errorsq);
>
> }
>
>
>
>
for iterator in range(istart; iend):
lin_estimate = y[istart] + ((y[iend] - y[istart]) * ((x[m] -
x[istart]) / (x[iend] - x[istart])))
errorsq += (lin_estimate - y[m]) * (lin_estimate - y[m])
return errorsq
> At the end the three values I want are mini, minj, mink;
> or x[mini], x[minj], x[mink]
>
>
> So how do I do this (or approach this) in Python?
>
> Loose Translation
>
> Kip
>
> ___
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> To unsubscribe or change subscription options:
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>
I'll look at it a little more later on, unless someone' is less rusty in C
and Python than I am.
--
Best Regards,
David Hutto
*CEO:* *http://www.hitwebdevelopment.com *
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Re: [Tutor] Traversing lists or getting the element you want.
On Sun, Feb 2, 2014 at 6:44 PM, David Hutto wrote:
>
>
>
> On Sun, Feb 2, 2014 at 3:46 PM, Kipton Moravec wrote:
>
>> I am new to Python, and I do not know how to traverse lists like I
>> traverse arrays in C. This is my first program other than "Hello World".
>> I have a Raspberry Pi and they say Python is the language of choice for
>> that little machine. So I am going to try to learn it.
>>
>>
>> I have data in the form of x, y pairs where y = f(x) and is non linear.
>> It comes from a .csv file.
>>
>> In this case x is an integer from 165 to 660 so I have 495 data sets.
>>
>> I need to find the optimal locations of three values of x to piecewise
>> linear estimate the function.
>>
>>
>> So I need to find i, j, k so 165 < i < j < k < 660 and the 4 line
>> segments [(165, f(165)), (i, f(i))], [(i, f(i)), (j, f(j))], [(j, f(j),
>> (k, f(k))], [(k, f(k)), (660, f(660))].
>>
>> So as you iterate through the minimize function below, you want something
> like this, I believe:
>
> if (165 < i) and (i < j) and (j < k) and (k < 660):
> print 'true'
> else:
> print 'false'
>
>
>> The value I need to minimize is the square of the difference between the
>> line estimate and the real value at each of the 495 points.
>>
>>
>> I can do this in C. To keep it simple to understand I will assume the
>> arrays x[] and y[] and minsum, mini, minj, and mink are global.
>>
>>
>> I have not tested this but this is what I came up with in C. Assuming
>> x[] and y[] are already filled with the right values.
>>
>>
>> int x[495];
>> double y[495];
>> max_elements = 495;
>> double minsum;
>> int mini, minj, mink
>>
>> #We define some vars before utilizing them x,and y are list comprehension
> # You said int for x, so it's created in ints, and y is in floats
> x = [num for num in range(0,496)]
> # You said double for y, so the it's created in floats, and x is an int
> list
> y = [float(num) for num in range(0,496)]
> i = 0
> j = 0
> k = 0
> max_elements = 495
> mini = 0
> minj = 0
> mink = 0
>
>
>> void minimize(int max_elements)
>>
>>
> def minimize(max_elements):
>
> {
>> minsum = 9.0; // big big number
>>
>>
> minsum = float(9.0) # used float just to show as double
>
>
>
>> for (i=2; i> for (j=i+2; j< max_elements -4; j++)
>> for (k=j+2; k< max_elements-2;k++)
>>
>
> for i in range(2,max_elements-6):
> print i
> for j in range(i+2,max_elements-4):
> print j
> for k in range(j+2,max_elements-2):
> print k
>
>
>> {
>> sum = error(0,i);
>> sum += error(i,j);
>> sum += error(j,k);
>> sum += error(k,495)
>>
>>
> sum = error(0,i)
> sum += error(i,j)
> sum += error(j,k)
> sum += error(k,495)
>
>
>> if (sum < minsum)
>> {
>> minsum = sum;
>> mini = i;
>> minj = j;
>> mink = k;
>> }
>> }
>> }
>>
>>
>
> if sum < minsum:
>
> minsum = sum
> mini = i
> minj = j
> mink = k
>
>
>>
>> double error(int istart, int iend)
>> {
>>
>>
> error(int istart, int iend):
>
>
>
>> // linear interpolation I can optimize but left
>> // it not optimized for clarity of the function
>>
>> int m;
>>
>> double lin_estimate;
>>
>> double errorsq;
>>
>> errorsq = 0;
>>
>>
> Forgot this part:
> m = 0
>
> lin_estimate = 0
>
> errorsq = float(0) #just to show double = float type again
>
> errorsq = 0
>
>
>
>> for (m=istart; m> {
>> lin_estimate = y[istart] + ((y[iend] - y[istart]) *
>>((x[m] - x[istart]) / (x[iend] - x[istart])));
>>
>> errorsq += (lin_estimate - y[m]) * (lin_estimate - y[m]);
>> }
>>
>> return (errorsq);
>>
>> }
>>
>>
>>
>>
>
> for iterator in range(istart; iend):
>
> lin_estimate = y[istart] + ((y[iend] - y[istart]) * ((x[m] -
> x[istart]) / (x[iend] - x[istart])))
>
> errorsq += (lin_estimate - y[m]) * (lin_estimate - y[m])
>
> return errorsq
>
>
>
>
>> At the end the three values I want are mini, minj, mink;
>> or x[mini], x[minj], x[mink]
>>
>>
>> So how do I do this (or approach this) in Python?
>>
>> Loose Translation
>
>>
>> Kip
>>
>> ___
>> Tutor maillist - Tutor@python.org
>> To unsubscribe or change subscription options:
>> https://mail.python.org/mailman/listinfo/tutor
>>
>
> I'll look at it a little more later on, unless someone' is less rusty in C
> and Python than I am.
>
> --
> Best Regards,
> David Hutto
> *CEO:* *http://www.hitwebdevelopment.com
> *
>
>
--
Best Regards,
David Hutto
*CEO:* *http://www.hitwebdevelopment.com *
Re: [Tutor] Traversing lists or getting the element you want.
Kind of sure this is the translation line for line:
#We define some vars before utilizing them x,and y are list comprehension
# You said int for x, so it's created in ints, and y is in floats
x = [num for num in range(0,496)]
# You said double for y, so the it's created in floats, and x is an int list
y = [float(num) for num in range(0,496)]
i = 0
j = 0
k = 0
max_elements = 495
mini = 0
minj = 0
mink = 0
def minimize(max_elements):
minsum = float(9.0) # used float just to show as double
for i in range(2,max_elements-6):
for j in range(i+2,max_elements-4):
for k in range(j+2,max_elements-2):
sum = error(0,i)
sum += error(i,j)
sum += error(j,k)
sum += error(k,495)
if sum < minsum:
minsum = sum
mini = i
minj = j
mink = k
def error(istart,iend):
m = 0
lin_estimate = 0
errorsq = float(0) #just to show double = float type again
errorsq = 0
lin_estimate = y[istart] + ((y[iend] - y[istart]) * ((x[m] - x[istart])
/ (x[iend] - x[istart])))
errorsq += (lin_estimate - y[m]) * (lin_estimate - y[m])
#print errorsq # insert print for quick in line debugging by
uncommenting
return errorsq
#Call function minimize
minimize(max_elements)
Don't forget the tabs , or spaces, and the forced indentation.
On Sun, Feb 2, 2014 at 6:44 PM, David Hutto wrote:
>
>
>
> On Sun, Feb 2, 2014 at 3:46 PM, Kipton Moravec wrote:
>
>> I am new to Python, and I do not know how to traverse lists like I
>> traverse arrays in C. This is my first program other than "Hello World".
>> I have a Raspberry Pi and they say Python is the language of choice for
>> that little machine. So I am going to try to learn it.
>>
>>
>> I have data in the form of x, y pairs where y = f(x) and is non linear.
>> It comes from a .csv file.
>>
>> In this case x is an integer from 165 to 660 so I have 495 data sets.
>>
>> I need to find the optimal locations of three values of x to piecewise
>> linear estimate the function.
>>
>>
>> So I need to find i, j, k so 165 < i < j < k < 660 and the 4 line
>> segments [(165, f(165)), (i, f(i))], [(i, f(i)), (j, f(j))], [(j, f(j),
>> (k, f(k))], [(k, f(k)), (660, f(660))].
>>
>> So as you iterate through the minimize function below, you want something
> like this, I believe:
>
> if (165 < i) and (i < j) and (j < k) and (k < 660):
> print 'true'
> else:
> print 'false'
>
>
>> The value I need to minimize is the square of the difference between the
>> line estimate and the real value at each of the 495 points.
>>
>>
>> I can do this in C. To keep it simple to understand I will assume the
>> arrays x[] and y[] and minsum, mini, minj, and mink are global.
>>
>>
>> I have not tested this but this is what I came up with in C. Assuming
>> x[] and y[] are already filled with the right values.
>>
>>
>> int x[495];
>> double y[495];
>> max_elements = 495;
>> double minsum;
>> int mini, minj, mink
>>
>> #We define some vars before utilizing them x,and y are list comprehension
> # You said int for x, so it's created in ints, and y is in floats
> x = [num for num in range(0,496)]
> # You said double for y, so the it's created in floats, and x is an int
> list
> y = [float(num) for num in range(0,496)]
> i = 0
> j = 0
> k = 0
> max_elements = 495
> mini = 0
> minj = 0
> mink = 0
>
>
>> void minimize(int max_elements)
>>
>>
> def minimize(max_elements):
>
> {
>> minsum = 9.0; // big big number
>>
>>
> minsum = float(9.0) # used float just to show as double
>
>
>
>> for (i=2; i> for (j=i+2; j< max_elements -4; j++)
>> for (k=j+2; k< max_elements-2;k++)
>>
>
> for i in range(2,max_elements-6):
> print i
> for j in range(i+2,max_elements-4):
> print j
> for k in range(j+2,max_elements-2):
> print k
>
>
>> {
>> sum = error(0,i);
>> sum += error(i,j);
>> sum += error(j,k);
>> sum += error(k,495)
>>
>>
> sum = error(0,i)
> sum += error(i,j)
> sum += error(j,k)
> sum += error(k,495)
>
>
>> if (sum < minsum)
>> {
>> minsum = sum;
>> mini = i;
>> minj = j;
>> mink = k;
>> }
>> }
>> }
>>
>>
>
> if sum < minsum:
>
> minsum = sum
> mini = i
> minj = j
> mink = k
>
>
>>
>> double error(int istart, int iend)
>> {
>>
>>
> error(int istart, int iend):
>
>
>
>> // linear interpolation I can optimize but left
>> // it not optimized for clarity of the function
>>
>> int m;
>>
>> double lin_estimate;
>>
>> double errorsq;
>>
Re: [Tutor] Traversing lists or getting the element you want.
Kipton Moravec Wrote in message:
> I am new to Python, and I do not know how to traverse lists like I
> traverse arrays in C. This is my first program other than "Hello World".
> I have a Raspberry Pi and they say Python is the language of choice for
> that little machine. So I am going to try to learn it.
>
>
> I have data in the form of x, y pairs where y = f(x) and is non linear.
> It comes from a .csv file.
>
Sounds to me that you've just got a y list; your x list has the
implicit assumption of being range (165,660)
> In this case x is an integer from 165 to 660 so I have 495 data sets.
>
> I need to find the optimal locations of three values of x to piecewise
> linear estimate the function.
>
You're making the unspoken assumption that each line starts and
ends exactly on a data point. That won't give you the minimum
error in general, but perhaps it is an extra oddball restriction
in the assignment.
>
> So I need to find i, j, k so 165 < i < j < k < 660 and the 4 line
> segments [(165, f(165)), (i, f(i))], [(i, f(i)), (j, f(j))], [(j, f(j),
> (k, f(k))], [(k, f(k)), (660, f(660))].
>
>
> The value I need to minimize is the square of the difference between the
> line estimate and the real value at each of the 495 points.
No it appears to be the sum of the squares.
>
>
> I can do this in C. To keep it simple to understand I will assume the
> arrays x[] and y[] and minsum, mini, minj, and mink are global.
>
That may seem to simplify the c but it's not pythonic. If a
function calculates 4 values, it should return 4 values,
presumably as a tuple.
>
> I have not tested this but this is what I came up with in C. Assuming
> x[] and y[] are already filled with the right values.
>
>
> int x[495];
> double y[495];
> max_elements = 495;
> double minsum;
> int mini, minj, mink
>
>
> void minimize(int max_elements)
>
> {
> minsum = 9.0; // big big number
>
> for (i=2; i for (j=i+2; j< max_elements -4; j++)
> for (k=j+2; k< max_elements-2;k++)
> {
> sum = error(0,i);
> sum += error(i,j);
> sum += error(j,k);
> sum += error(k,495)
>
> if (sum < minsum)
> {
> minsum = sum;
> mini = i;
> minj = j;
> mink = k;
> }
> }
> }
>
>
> double error(int istart, int iend)
> {
>
> // linear interpolation I can optimize but left
> // it not optimized for clarity of the function
>
> int m;
>
> double lin_estimate;
>
> double errorsq;
>
> errorsq = 0;
>
> for (m=istart; m {
> lin_estimate = y[istart] + ((y[iend] â y[istart]) *
>((x[m] â x[istart]) / (x[iend] â x[istart])));
>
> errorsq += (lin_estimate â y[m]) * (lin_estimate â y[m]);
> }
>
> return (errorsq);
>
> }
>
>
>
> At the end the three values I want are mini, minj, mink;
> or x[mini], x[minj], x[mink]
>
>
> So how do I do this (or approach this) in Python?
>
>
for (i=2; i___
Tutor maillist - Tutor@python.org
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Re: [Tutor] Traversing lists or getting the element you want.
On Sun, Feb 02, 2014 at 02:46:38PM -0600, Kipton Moravec wrote: > I am new to Python, and I do not know how to traverse lists like I > traverse arrays in C. You can do this, but normally shouldn't: data = [2, 4, 8, 16, 32] for i in range(0, len(data)): x = data[i] print(x) That is a more-or-less exact translation of what you might do in a language like C or Pascal. But in Python, it's not considered good form. (Although, if you are doing a direct translation of some C code, it might be acceptable.) Instead, you should iterate directly over the elements of the list: data = [2, 4, 8, 16, 32] for x in data: print(x) (Python's for-loop is what some other languages call "for-each".) If you need the index as well, you can do this: data = [2, 4, 8, 16, 32] for i, x in enumerate(data): print(i, x) The rest of your question seems pretty interesting, unfortunately I don't have time to get into it now. Good luck! -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] sorting and writing to data file
On 02/02/2014 04:08 AM, adrian wrote:
Hello community,
Newbie here. I have a data (.dat) file with integers (2,9,1,5,7,3,9) in it just
as shown.
My instructions are to sort the numbers and rewrite them back to the data file.
*here is my code:**
*
lab3int=[2,9,1,5,7,3,9]
lab3int.sort()
print(lab3int)
lab3int=open('lab3int.dat','w')
lab3int.write()
lab3int.close()
*here is my error message:*
[1, 2, 3, 5, 7, 9, 9]
Traceback (most recent call last):
File "lab3int.py", line 5, in
lab3int.write()
TypeError: function takes exactly 1 argument (0 given)
I know that it is telling me that my error is in line #5. If I put anything in
the () for lab3int.write function, then that appears in my data file. however,
I am looking to just put the re-sorted integers back into the data file without
having to manually type each integer manually. Is there something that i can
put into the lab3int.write() to make that happen?
Hope my problem is clear, Thanks people
Do you realise you are calling two different very objects, a list of nums and a
file, with the same name 'lab3int'?
d
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Re: [Tutor] most useful ide
On 02/02/2014 09:10 PM, Pierre Dagenais wrote: On 14-02-02 01:16 PM, Kodiak Firesmith wrote: Pycharm is nice for bigger projects (since tou can collapse any section); but it's crazy resource intensive. For Linux Gedit can be made very nice I prefer Geany as it will run my code with a click of the mouse. geany is my favorite editor as well I'd use gedit for its simplicity, but cannot survive an editor without the 'duplicate' command (ctrl-d). d ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
