Re: [newbie] copying identical list for a function argument
Op maandag 3 februari 2014 23:19:39 UTC+1 schreef Steven D'Aprano: On Mon, 03 Feb 2014 13:36:24 -0800, Jean Dupont wrote: I have a list like this: [1,2,3] The argument of my function should be a repeated version e.g. [1,2,3],[1,2,3],[1,2,3],[1,2,3] (could be a different number of times repeated also) what is the prefered method to realize this in Python? I don't really understand your question. It could mean any of various things, so I'm going to try to guess what you mean. If my guesses are wrong, please ask again, giving more detail, and possibly an example of what you want to do and the result you expect. I think you mean that you have some function that needs to take (say) five arguments, and you want to avoid writing: result = function([1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 23], [1, 2, 3]) because it's too easy to make a mistake (as I did, deliberately, above -- can you see it?). If my guess is correct, try this: mylist = [1, 2, 3] result = function(mylist, mylist, mylist, mylist, mylist) That's perfectly reasonable for two or three arguments, but not so much for five. Instead, here's a trick: first we make five identical references to the same list: [mylist]*5 # same as [mylist, mylist, mylist, mylist, mylist] then expand them as arguments to the function: mylist = [1, 2, 3] list_of_lists = [mylist]*5 result = function(*list_of_lists) (The * operator means multiplication when used between two arguments, and inside a function call a leading * also does argument expansion.) But wait... there's something slightly weird here. Even though there are five distinct references to mylist, they're all the same list! Change one, change all. This may be what you want, or it may be a problem. Hard to tell from your question. Think about references as being a little bit like names. A *single* person could be known as son, Dad, Mr Obama, Barack, Mr President, POTUS, and more. In this case, we have a single list, [1, 2, 3], which is known by six references: the name mylist, and five additional references list_of_lists index 0, list_of_lists index 1, and so on up to list_of_lists index 4. We can prove that they all refer to the same list by running a bit of code in the interactive interpreter: py mylist = [1, 2, 3] py list_of_lists = [mylist]*5 py list_of_lists [[1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3]] py mylist.append(99) py list_of_lists [[1, 2, 3, 99], [1, 2, 3, 99], [1, 2, 3, 99], [1, 2, 3, 99], [1, 2, 3, 99]] So rather than having five references to the same, identical, list, you might want five *copies*. You can copy a list using slicing: mylist = [1, 2, 3] copy = mylist[:] Instead of using list multiplication to repeat five identical lists, we make five copies using a list comprehension: list_of_lists = [mylist[:] for i in range(5)] then expand it in the function call as before: result = function(*list_of_lists) Hope this helps, Yes it does, thanks a lot to you and all the others who responded, the missing link which until now I wasn't aware of but which was essential for the solution was the * in result = function(*list_of_lists) kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] making rows of table with discrete values for different number systems
Op maandag 3 februari 2014 20:50:04 UTC+1 schreef Asaf Las: On Monday, February 3, 2014 9:37:36 PM UTC+2, Jean Dupont wrote: Op maandag 3 februari 2014 16:34:18 UTC+1 schreef Asaf Las: Of course you don't have to, but I'm curious and learn well by examples :-( Hi Jean Don't get me wrong i did not mean to be rude (was joking) - i think if you will do it yourself that will be very good for you - you can learn a lot from that as i did not very long time ago. My apologies for inconvenience. no hard feelings, anyway I am programming it myself using normal functions, when I have finished it I'll post it, then maybe you can do it with lamba-notation, it could be interesting to compare execution times for the two approaches kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] making rows of table with discrete values for different number systems
Op maandag 3 februari 2014 02:56:43 UTC+1 schreef Asaf Las: On Sunday, February 2, 2014 10:51:15 PM UTC+2, Jean Dupont wrote: Op zondag 2 februari 2014 19:10:32 UTC+1 schreef Peter Otten: I'm looking for an efficient method to produce rows of tables like this: jean you can also try to make below universal for all needed bases: m = lambda m, n: 1 if m n else 0 k = [[ m(x,8) , m(x, 4), m(x, 2), m(x, 1)] for x in range(10)] print (k) Dear Asaf, I'm not at ease with lamba-notation, could you show me how to modify your example for the base 3 case? I guess then it will be much clearer to me thanks in advance jean -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] making rows of table with discrete values for different number systems
Op zondag 2 februari 2014 19:07:38 UTC+1 schreef Roy Smith: In article 515e582f-ed17-4d4e-9872-f07f1fda6...@googlegroups.com, Jean Dupont jeandupont...@gmail.com wrote: I'm looking for an efficient method to produce rows of tables like this: for base 2 0 0 0 0 0 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 . . . 1 1 1 1 for base 3 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 2 0 0 0 0 1 0 0 0 0 0 1 1 0 0 0 0 1 2 . . 2 2 2 2 2 2 This sounds like a homework problem :-) As you can see the rows are always twice the size of the base Why? I _don't_ need to have all rows available together in one array which would become too large for higher value number bases. It's sufficient to produce one row after the other, as I will do further data manipulation on such a row immediately. What I get out of that is that you don't want to just print them, you want to have some function which returns all the generated rows in order. The way to do that is with the yield statement. Take a look at https://wiki.python.org/moin/Generators for some discussion on how that works. Actually, http://stackoverflow.com/questions/231767/ looks like an even better discussion. Does that help you any? Thanks, I'll try to figure out what yield does kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
[newbie] troubles with tuples
I'm looking at the way to address tuples e.g. tup2 = (1, 2, 3, 4, 5, 6, 7 ); As I found out indices start with 0 in Python, so tup2[0] gives me 1, the first element in the tuple as expected tup2[1] gives me 2, the second element in the tuple as expected now here comes what surprises me: tup2[0:1] does not give me the expected (1,2) but (2,) what is the reason for this and how then should one get the first and the second element of a tuple? Or the 3rd until the 5th? thanks in advance and kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] troubles with tuples
Op maandag 3 februari 2014 18:06:46 UTC+1 schreef Rustom Mody: On Monday, February 3, 2014 10:20:31 PM UTC+5:30, Jean Dupont wrote: I'm looking at the way to address tuples e.g. tup2 = (1, 2, 3, 4, 5, 6, 7 ); As I found out indices start with 0 in Python, so tup2[0] gives me 1, the first element in the tuple as expected tup2[1] gives me 2, the second element in the tuple as expected now here comes what surprises me: tup2[0:1] does not give me the expected (1,2) but (2,) Python 2.7.6 (default, Jan 11 2014, 17:06:02) [GCC 4.8.2] on linux2 Type help, copyright, credits or license for more information. tup2=(1,2,3,4,5,6,7) tup2[0:1] (1,) So assuming you meant (1,) and wrote (2,) :-) what is the reason for this and how then should one get the first and the second element of a tuple? Or the 3rd until the 5th? Generally ranges in python are lower-inclusive upper-exclusive What some math texts write as [lo, hi) So if you want from index 1 to 2-inclusive it is 1 to 3 exclusive tup2[0:2] See for motivations http://www.cs.utexas.edu/~EWD/transcriptions/EWD08xx/EWD831.html And one more surprising thing to note is that negatives count from the end Thank you (and the others) for making this logical kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] making rows of table with discrete values for different number systems
Op maandag 3 februari 2014 16:34:18 UTC+1 schreef Asaf Las: On Monday, February 3, 2014 5:05:40 PM UTC+2, Jean Dupont wrote: Op maandag 3 februari 2014 02:56:43 UTC+1 schreef Asaf Las: On Sunday, February 2, 2014 10:51:15 PM UTC+2, Jean Dupont wrote: Op zondag 2 februari 2014 19:10:32 UTC+1 schreef Peter Otten: I'm looking for an efficient method to produce rows of tables like this: jean you can also try to make below universal for all needed bases: m = lambda m, n: 1 if m n else 0 k = [[ m(x,8) , m(x, 4), m(x, 2), m(x, 1)] for x in range(10)] print (k) Dear Asaf, I'm not at ease with lamba-notation, could you show me how to modify your example for the base 3 case? I guess then it will be much clearer to me thanks in advance jean I don't have to - use normal functions instead :-) Of course you don't have to, but I'm curious and learn well by examples :-( -- https://mail.python.org/mailman/listinfo/python-list
[newbie] copying identical list for a function argument
I have a list like this: [1,2,3] The argument of my function should be a repeated version e.g. [1,2,3],[1,2,3],[1,2,3],[1,2,3] (could be a different number of times repeated also) what is the prefered method to realize this in Python? any help would be really appreciated kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
[newbie] making rows of table with discrete values for different number systems
I'm looking for an efficient method to produce rows of tables like this: for base 2 0 0 0 0 0 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 . . . 1 1 1 1 for base 3 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 2 0 0 0 0 1 0 0 0 0 0 1 1 0 0 0 0 1 2 . . 2 2 2 2 2 2 As you can see the rows are always twice the size of the base I _don't_ need to have all rows available together in one array which would become too large for higher value number bases. It's sufficient to produce one row after the other, as I will do further data manipulation on such a row immediately. If someone here could suggest best practices to perform this kind of operations,I'd really appreciate it very much kind regards and thanks in advance jean -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] making rows of table with discrete values for different number systems
Op zondag 2 februari 2014 19:10:32 UTC+1 schreef Peter Otten: Jean Dupont wrote: I'm looking for an efficient method to produce rows of tables like this: for base 2 0 0 0 0 0 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 . . . 1 1 1 1 for base 3 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 2 0 0 0 0 1 0 0 0 0 0 1 1 0 0 0 0 1 2 . . 2 2 2 2 2 2 As you can see the rows are always twice the size of the base I _don't_ need to have all rows available together in one array which would become too large for higher value number bases. It's sufficient to produce one row after the other, as I will do further data manipulation on such a row immediately. If someone here could suggest best practices to perform this kind of operations,I'd really appreciate it very much Have a look at itertools.product(): import itertools for row in itertools.product(range(2), repeat=4): ... print(*row) ... 0 0 0 0 0 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 0 1 0 1 0 1 1 0 0 1 1 1 1 0 0 0 1 0 0 1 1 0 1 0 1 0 1 1 1 1 0 0 1 1 0 1 1 1 1 0 1 1 1 1 Thanks for the suggestion I'm going to look into it further kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] advice and comment wanted on first tkinter program
Op woensdag 22 januari 2014 16:43:21 UTC+1 schreef Alister: On Wed, 22 Jan 2014 06:45:53 -0800, Jean Dupont wrote: Op maandag 20 januari 2014 10:17:15 UTC+1 schreef Alister: On Sun, 19 Jan 2014 20:04:05 -0800, Jean Dupont wrote: Op zaterdag 18 januari 2014 16:12:41 UTC+1 schreef Oscar Benjamin: On 18 January 2014 14:52, Jean Dupont jeandupont...@gmail.com wrote: Thanks Peter and Terry Jan for the useful suggestions. One thing which I find a bit weird: when asking for Python-help concerning raspberry Personally use Geany stand alone and not under idle, pressing F5 should save run the code you are currently editing. Would running under idle give any other benefits? I don't know yet, but I just wanted to try out which of the following three I'd like best: 1. idle+leafpad 2. idle+geany 3. plain geany It's normal for a newbie to start with (1) as that is the default on raspbian, however I still don't understand why (2) does not work... When I play with my Pi I tend to use another computer for all my editing (sshfs is a quick easy way for me to mount the necessary parts of the PI file system so I don't have to keep transferring files) Thanks for the suggestion, I'm going to try it out kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] advice and comment wanted on first tkinter program
Op woensdag 22 januari 2014 15:45:53 UTC+1 schreef Jean Dupont: Op maandag 20 januari 2014 10:17:15 UTC+1 schreef Alister: On Sun, 19 Jan 2014 20:04:05 -0800, Jean Dupont wrote: Op zaterdag 18 januari 2014 16:12:41 UTC+1 schreef Oscar Benjamin: On 18 January 2014 14:52, Jean Dupont jeandupont...@gmail.com wrote: Thanks Peter and Terry Jan for the useful suggestions. One thing which I find a bit weird: when asking for Python-help concerning raspberry pi code or problems, a lot of people don't seem to be interested in helping out, that's of course their choice, but maybe they don't seem to be aware the raspberry pi is often the motivation for starting to learn to program in Python. And as such such a reaction is a bit disappointing. Hi Jean, What makes you say that? Did you previously ask questions about Rasberry Pi code on this list? It was not about code but about python-coding in IDLE (that's the default on raspbian): I started a thread [newbie] starting geany from within idle does not work both here and in the raspberry pi forum. I just wondered why I never got an answer concerning that topic. If you did I wouldn't have answered those questions because I've never used a Raspberry Pi and know nothing about them (except that they encourage using Python somehow). I think that there's actually a list that is specifically for Raspberry Pi Python questions that might be more helpful although I don't know what it is... Here is the url to that forum http://www.raspberrypi.org/forum/ kind regards, jean Personally use Geany stand alone and not under idle, pressing F5 should save run the code you are currently editing. Would running under idle give any other benefits? I don't know yet, but I just wanted to try out which of the following three I'd like best: 1. idle+leafpad 2. idle+geany 3. plain geany It's normal for a newbie to start with (1) as that is the default on raspbian, however I still don't understand why (2) does not work... I finally found out where I was wrong: leafpad is _not_ the default choice in IDLE, IDLE has its own built in editor and IDLE does not allow to use another editor. The confusion stemmed from the properties I got when right clicking on the IDLE-icon on the raspbian desktop, which shows Open with and then suggests the default choice is Leafpad and Geany as a second choice, it has however nothin to do with IDLE as such. kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] advice and comment wanted on first tkinter program
Op maandag 20 januari 2014 10:17:15 UTC+1 schreef Alister: On Sun, 19 Jan 2014 20:04:05 -0800, Jean Dupont wrote: Op zaterdag 18 januari 2014 16:12:41 UTC+1 schreef Oscar Benjamin: On 18 January 2014 14:52, Jean Dupont jeandupont...@gmail.com wrote: Thanks Peter and Terry Jan for the useful suggestions. One thing which I find a bit weird: when asking for Python-help concerning raspberry pi code or problems, a lot of people don't seem to be interested in helping out, that's of course their choice, but maybe they don't seem to be aware the raspberry pi is often the motivation for starting to learn to program in Python. And as such such a reaction is a bit disappointing. Hi Jean, What makes you say that? Did you previously ask questions about Rasberry Pi code on this list? It was not about code but about python-coding in IDLE (that's the default on raspbian): I started a thread [newbie] starting geany from within idle does not work both here and in the raspberry pi forum. I just wondered why I never got an answer concerning that topic. If you did I wouldn't have answered those questions because I've never used a Raspberry Pi and know nothing about them (except that they encourage using Python somehow). I think that there's actually a list that is specifically for Raspberry Pi Python questions that might be more helpful although I don't know what it is... Here is the url to that forum http://www.raspberrypi.org/forum/ kind regards, jean Personally use Geany stand alone and not under idle, pressing F5 should save run the code you are currently editing. Would running under idle give any other benefits? I don't know yet, but I just wanted to try out which of the following three I'd like best: 1. idle+leafpad 2. idle+geany 3. plain geany It's normal for a newbie to start with (1) as that is the default on raspbian, however I still don't understand why (2) does not work... kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] advice and comment wanted on first tkinter program
Op maandag 20 januari 2014 07:24:31 UTC+1 schreef Chris Angelico: On Mon, Jan 20, 2014 at 3:04 PM, Jean Dupont jeandupont...@gmail.com wrote: I started a thread [newbie] starting geany from within idle does not work both here and in the raspberry pi forum. I just wondered why I never got an answer concerning that topic. I saw that thread. It looked like a R-Pi problem, not a Python one, so I didn't respond because I don't have an R-Pi. If you get no response on the R-Pi forum, you might want to see if you can duplicate the issue on a desktop computer - preferably on Win/Mac/Lin, as those are the platforms most people use. That, with exact steps to repro (which it looks like you gave for the R-Pi, though again I can't verify), would get some interest. I did try to do the same on my linux desktop computer, but the problem is, it has another desktop environment (KDE4). In the rpi-environment it is possible (but it doesn't work) to change the default IDLE-editor by right-clicking the idle-icon and choosing geany in stead of leafpad, however the same can't be done in KDE4, I hoped to find a similar setting once running IDLE in Options--Configure IDLE, but nothing there neither. I also looked unsuccessfuly in the .idlerc-directory for a config-file. Hence my initial question. kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] advice and comment wanted on first tkinter program
Op zaterdag 18 januari 2014 16:12:41 UTC+1 schreef Oscar Benjamin: On 18 January 2014 14:52, Jean Dupont jeandupont...@gmail.com wrote: Thanks Peter and Terry Jan for the useful suggestions. One thing which I find a bit weird: when asking for Python-help concerning raspberry pi code or problems, a lot of people don't seem to be interested in helping out, that's of course their choice, but maybe they don't seem to be aware the raspberry pi is often the motivation for starting to learn to program in Python. And as such such a reaction is a bit disappointing. Hi Jean, What makes you say that? Did you previously ask questions about Rasberry Pi code on this list? It was not about code but about python-coding in IDLE (that's the default on raspbian): I started a thread [newbie] starting geany from within idle does not work both here and in the raspberry pi forum. I just wondered why I never got an answer concerning that topic. If you did I wouldn't have answered those questions because I've never used a Raspberry Pi and know nothing about them (except that they encourage using Python somehow). I think that there's actually a list that is specifically for Raspberry Pi Python questions that might be more helpful although I don't know what it is... Here is the url to that forum http://www.raspberrypi.org/forum/ kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] advice and comment wanted on first tkinter program
Op vrijdag 17 januari 2014 22:40:42 UTC+1 schreef Terry Reedy: On 1/17/2014 8:20 AM, Jean Dupont wrote: Dear all, I made a simple gui with tkinter. I can imagine there are things which I did which are not optimal. So what I ask is to comment on my code preferable with snippets of code which show how to do improve my code. #!/usr/bin/env python import Tkinter 1. import Tkinter as tk Besides saving a bit of writing and reading time later, this makes any future conversion to 3.x easier. import tkinter as tk 2. add a few spaces to demarcate blocks of code. import time import RPi.GPIO as GPIO 2. add a few spaces to demarcate blocks of code, such as here GPIO.setmode(GPIO.BOARD) GPIO.setup(26,GPIO.OUT) GPIO.setup(24,GPIO.OUT) #hardware : connect 2 leds: #board-pin 26 on/off led; control with buttons #board-pin 24 led with pwm dimming and frequency; control via sliders and here top = Tkinter.Tk() top.geometry(600x400+310+290) This looks strange somehow, but if it works... label1 = Label(top,relief=RAISED,bg = #EFF980,font=(Helvetica,14),height = 1, width = 15) In calls, put spaces after , but not before and after =. For other suggestions, see http://www.python.org/dev/peps/pep-0008/ I suspect that the above is one line in your code and the bad wrapping a result of mis-spacing. The following is also one line, but easer to read as spaces separate argument chunks label1 = Label(top, relief=RAISED, bg=#EFF980, font=(Helvetica,14), height=1, width=15) and the wrapping, if any, does not break up an arg chunk. Some people advocate defining an App class, but Tk and tkinter, even though object method based, allow the straightforward imperative style you have used. I agree with Peter: First and foremost a program has to do what the author wants it to do. Everything else is secondary. But a bit of styling will make reading and changing easier. -- Terry Jan Reedy Thanks Peter and Terry Jan for the useful suggestions. One thing which I find a bit weird: when asking for Python-help concerning raspberry pi code or problems, a lot of people don't seem to be interested in helping out, that's of course their choice, but maybe they don't seem to be aware the raspberry pi is often the motivation for starting to learn to program in Python. And as such such a reaction is a bit disappointing. kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
[newbie] advice and comment wanted on first tkinter program
Dear all, I made a simple gui with tkinter. I can imagine there are things which I did which are not optimal. So what I ask is to comment on my code preferable with snippets of code which show how to do improve my code. #!/usr/bin/env python import Tkinter import time import RPi.GPIO as GPIO GPIO.setmode(GPIO.BOARD) GPIO.setup(26,GPIO.OUT) GPIO.setup(24,GPIO.OUT) #hardware : connect 2 leds: #board-pin 26 on/off led; control with buttons #board-pin 24 led with pwm dimming and frequency; control via sliders top = Tkinter.Tk() top.geometry(600x400+310+290) var1 = DoubleVar() var2 = DoubleVar() i=0 p=GPIO.PWM(24,1) p.start(50) def btn_on_cmd(): text3.configure(bg = #00FF00) text3.delete(0.1,END) text3.insert(0.1,ON ) GPIO.output(26,True) def btn_off_cmd(): text3.configure(bg = #FF4000) text3.delete(0.1,END) text3.insert(0.1,OFF) GPIO.output(26, False) def timer0(): global i i=i+1 text1.delete(0.1,END) text1.insert(4.2,Timer: + str(i)) label1.configure(text=time.strftime(%H:%M:%S)) top.after(1000, timer0) def Set_PWM(var1): DC = float(var1) p.ChangeDutyCycle(DC) def Set_FREQ(var2): FR = float(var2) p.ChangeFrequency(FR) btn_on = Button(top, text =On, command = btn_on_cmd) btn_on.place(x=10,y=100) btn_off = Button(top, text =Off, command = btn_off_cmd) btn_off.place(x=100,y=100) text1 =Text(top, bg = #009BFF, font=(Helvetica,14), height = 1, width = 15) text1.place(x=5,y=5) text3=Text(top, bg = red, font=(Helvetica,12),height = 1, width = 4) text3.place(x=60,y=60) label1 = Label(top,relief=RAISED,bg = #EFF980,font=(Helvetica,14),height = 1, width = 15) label1.place(x=5,y=350) label2= Label(top,relief=RAISED,bg = #BFBFBF,font=(Helvetica,10),height = 1, text= Freq (Hz)) label2.place(x=420,y=320) label3= Label(top,relief=RAISED,bg = #BFBFBF,font=(Helvetica,10),height = 1, text= DC %) label3.place(x=520,y=320) slider1 = Scale(top,variable = var1,length = 300,resolution = 1,command = Set_PWM) slider1 = Scale(top,variable = var1,length = 300,resolution = 1,command = Set_PWM) slider1.place(x=500,y=5) slider1.set(50) slider2 = Scale(top,variable = var2,length = 300,from_= 0.1, to = 50,resolution = 0.1,command = Set_FREQ) slider2.place(x=400,y=5) slider2.set(2) timer0() top.mainloop() GPIO.cleanup() thanks in advance jean -- https://mail.python.org/mailman/listinfo/python-list
[newbie] starting geany from within idle does not work
I'm using the latest Raspbian on a Raspberry Pi and I'd like to start IDLE so that it uses Geany instead of Leafpad. This seems at first sight a trivial task: Perform a rightmouse click on the IDLE-icon--Open with: Geany (in stead of the default Leafpad)--OK LXTerminal--lxpanelctl restart However if I then click on IDLE followed by File--New Window a Leafpad-session is opened and not a Geany-session Is there a workaround for it? thanks in advance jean p.s. I posted this question before in the Raspberry Pi forum but nobody seems to know the answer -- https://mail.python.org/mailman/listinfo/python-list
[newbie] problem with data (different behaviour between batch and interactive use)
I have some data which is presented in the following format to me:
+3.874693E-01,+9.999889E-03,+9.91E+37,+1.876595E+04,+3.994000E+04
I'm only interested in the first two fields i.e.
+3.874693E-01,+9.999889E-03
If I start python interactively I can separate the fields as follows:
measurement=+3.874693E01,+9.999889E03,+9.91E+37,+1.876595E+04,+3.994000E+04
print measurement[0]
0.3874693
print measurement[1]
0.00889
If however I run a script with the same commands I get something different:
The script does this:
measurement=serkeith.readline().replace('\x11','').replace('\x13','').replace('\x0d','\n')
print measurement[0]
+
print measurement[1]
3
can anyone here tell me what I'm doing wrong and how to do it correctly
thanks
jean
--
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Re: convert perl-script for voltcraft voltmeter to python [newbie]
On 8 feb, 01:26, Dietmar Schwertberger n...@schwertberger.de wrote: Am 03.02.2012 14:11, schrieb Jean Dupont: As my request might have been too much asked, I have started doing some coding myself. I'm in doubt about the readline statement -which doesn't show anything received- as the meter sends continuously streams of 11 bytes Is there a way to just monitor with python what is arriving at a serial port? Some time ago I started working on reading data from a VC940. I would assume that the protocol is the same. Please find below the code that will return the raw values from a VC940 (tested on a classical RS232 port, but probably will work on USB-RS232 converters as well). If you don't get anything, then you should check whether your USB converter is supplying voltage on the DTR pin once you have called self.serial.setDTR(1). You have the description how to decode the values? E.g. the string 0003:1401 translates to 0.3 Ohms. I did not implement anything else, as I just wanted to be sure that I could read the values, but I never needed to... Regards, Dietmar import serial import time class VC940(object): def __init__(self, port=COM3): self.port = port self.serial=serial.Serial(port,2400, bytesize=7, parity=N, stopbits=1, timeout=1.5, xonxoff=0, rtscts=0, dsrdtr=None) self.serial.setRTS(0) self.serial.setDTR(0) def _read_raw_value(self): timeout = True for n in range(5): self.serial.flushInput() self.serial.setDTR(1) data = self.serial.read(11) self.serial.setDTR(0) if data.endswith(\r\n) and len(data)==11: return data if not data: raise ValueError, communication timeout raise ValueError, could not read data from port if __name__==__main__: vc = VC940() while True: print vc._read_raw_value() Wow, this is great, it works like a charm. Thanks a lot! Jean -- http://mail.python.org/mailman/listinfo/python-list
Re: how to read serial stream of data [newbie]
On 7 feb, 06:07, Roy Smith r...@panix.com wrote: In article e84f3af4-da6d-4ae9-8974-54354ec16...@b18g2000vbz.googlegroups.com, Jean Dupont jeandupont...@gmail.com wrote: I'd like to read in a stream of data which looks like this: the device sends out a byte-string of 11 bytes roughly every second: B0B0B0B0B03131B0B50D8A B0B0B0B0B03131B0B50D8A B0B0B031B63131B0310D8A B0B034B3323432B3310D8A B0B03237B53432B3310D8A . . . As you see every string is ended by 0D8A How can this be accomplished in Python? The basic idea would be to open your datastream in binary mode (http://docs.python.org/library/functions.html#open), then use read(11) to read exactly 11 bytes into a string. Depending on what the 11 bytes are, you might want to use the struct module (http://docs.python.org/library/struct.html) to extract the data in a more useful form. Thank you very much for taking the time to reply. I'm really completely new to python and all help is really very welcome. In the documentation I read that to open the datastream binary I need to add the option b this is how far I got until now: #!/usr/bin/python import serial, time, os voltport='/dev/ttyUSB2' print Enter a filename:, filename = raw_input() voltdata = open(filename,'wb') ser2 = serial.Serial(voltport, 2400, 8, serial.PARITY_NONE, 1, rtscts=0, dsrdtr=0, timeout=15) ser2.setDTR(level=True) print State of DSR-line: , ser2.getDSR() #the following line was added because I want to be sure that all parameters are set the same as under a working application for the same device os.system(stty -F31:0:bbb: 0:0:0:0:0:0:0:1:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0) print Opening + ser2.portstr s =ser2.read(11) #read up to 11bytes voltdata.write(s) ser2.close() voltdata.close() However the above code doesn't fill my file with data, I guess the data should also be flushed somewhere in the code but I'm unsure where to do that. A futher consideration: because the device sends its data continuously I guess I'd have to use the byte sequence 0D8A of the previously sent data string as an indicator that the next 9 bytes are those I really want and put those in a string which than coudl be written to the file all help welcome Jean -- http://mail.python.org/mailman/listinfo/python-list
Re: how to read serial stream of data [newbie]
On 7 feb, 15:04, Heiko Wundram modeln...@modelnine.org wrote: Am 07.02.2012 14:48, schrieb Antti J Ylikoski: On 7.2.2012 14:13, Jean Dupont wrote: ser2 = serial.Serial(voltport, 2400, 8, serial.PARITY_NONE, 1, rtscts=0, dsrdtr=0, timeout=15) In Python, if you want to continue the source line into the next text line, you must end the line to be continued with a backslash '\'. Absolutely not true, and this is bad advice (stylistically). When (any form of) brackets are open at the end of a line, Python does not start a new command on the next line but rather continues the backeted content. So: ser2 = serial.Serial(voltport, 2400, 8, serial.PARITY_NONE, 1, rtscts=0, dsrdtr=0, timeout=15) is perfectly fine and certainly the recommended way of putting this. Adding the backslash-continuation is always _possible_, but only _required_ when there are no open brackets. So: x = hello \ test is equivalent to: x = (hello test) in assigning: x = hello test -- --- Heiko. Hello to all who gave advice concerning the line continuation, in fact this was not a real problem but happened by accident copying and pasting my program lines. Advice concerning the empty file would of course also be very much appreciated. thanks, Jean -- http://mail.python.org/mailman/listinfo/python-list
Re: convert perl-script for voltcraft voltmeter to python [newbie]
On 7 feb, 05:21, Terry Reedy tjre...@udel.edu wrote:
On 2/2/2012 3:57 PM, Jean Dupont wrote:
I'd like to read in the output of a voltcraft vc960 voltmeter
connected to a usb-port.
I found the perl-script below but I'd like to accomplish the same with
python:
The script below is for an old-fashioned, slow, multiple-pin serial
port, not usb. I don't know anything about interfacing through usb.
Recheck what the voltmeter actually connects to.
The voltmeter uses an optical rs232-connection, that is good enough
technology for this purpose. But as I don't have a computer with real
rs232 ports I use a rs232toUSB adapter which presents itself to the
linux-computer as /dev/ttyUSBx.
I guess I have to use the module serial but I don't know how I should
set the serial parameters so they are the same as in the perl-script.
Could someone supply me the command for setting the serial-parameters
correctly in Python?
Last I know, pyserial is also for old serial ports. Setting the
properties should be pretty obvious from the manual or code.
It is not so obvious as you might think, one reason being the
handshake line(s?) are used in an unconvential way to supply power to
the rs232-optical interface
There are also python usb
modules.http://sourceforge.net/projects/mysql-python/?source=directory
I followed this link but all I found was something concerning
mysql...???
anyway, thanks for trying to help
Jean
#!/usr/bin/perl
use strict;
use warnings;
use Device::SerialPort;
die(Usage: $0 /dev/ttyS0\n) unless $#ARGV == 0;
my ($devicepath) = @ARGV;
my $port = new Device::SerialPort($devicepath);
die Couldn't open serial port if ! defined $port;
$port-baudrate(2400);
$port-databits(8);
$port-parity(none);
$port-stopbits(1);
$port-handshake(none);
$port-rts_active(0);
$port-dtr_active(1);
#$port-read_char_time(5); # wait 5ms per character
$port-read_const_time(200); # 0.2 second per unfulfilled read
call
$| = 1; # autoflush STDOUT
while(1) {
my ($nin, $in) = $port-read(255);
print $in;
}
$port-close;
--
Terry Jan Reedy
--
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convert perl-script for voltcraft voltmeter to python [newbie]
I'd like to read in the output of a voltcraft vc960 voltmeter
connected to a usb-port.
I found the perl-script below but I'd like to accomplish the same with
python:
I guess I have to use the module serial but I don't know how I should
set the serial parameters so they are the same as in the perl-script.
Could someone supply me the command for setting the serial-parameters
correctly
in Python?
thanks
Jean
#!/usr/bin/perl
use strict;
use warnings;
use Device::SerialPort;
die(Usage: $0 /dev/ttyS0\n) unless $#ARGV == 0;
my ($devicepath) = @ARGV;
my $port = new Device::SerialPort($devicepath);
die Couldn't open serial port if ! defined $port;
$port-baudrate(2400);
$port-databits(8);
$port-parity(none);
$port-stopbits(1);
$port-handshake(none);
$port-rts_active(0);
$port-dtr_active(1);
#$port-read_char_time(5); # wait 5ms per character
$port-read_const_time(200); # 0.2 second per unfulfilled read
call
$| = 1; # autoflush STDOUT
while(1) {
my ($nin, $in) = $port-read(255);
print $in;
}
$port-close;
--
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Re: convert perl-script for voltcraft voltmeter to python [newbie]
As my request might have been too much asked, I have started doing
some coding myself.
I'm in doubt about the readline statement -which doesn't show anything
received- as the meter sends continuously streams of 11 bytes
Is there a way to just monitor with python what is arriving at a
serial port?
#!/usr/bin/python
#version 1-2-2012, script to read data from voltcraft vc940-meter
import serial, time, os
voltport='/dev/ttyUSB2'
print Be sure the Voltcraft is connected to ttyUSB2
print Enter a filename:,
filename = raw_input()
voltdata = open(filename,'w')
ser2 = serial.Serial(voltport, 2400, 8, serial.PARITY_NONE, 1,
timeout=15)
print rs-232 parameters of Voltcraft: , ser2
print Opening + ser2.portstr
received=ser2.readline()
print received
print Goodbye, data logged in file:
print filename
ser2.close()
# Close file
voltdata.close()
On 2 feb, 21:57, Jean Dupont jeandupont...@gmail.com wrote:
I'd like to read in the output of a voltcraft vc960 voltmeter
connected to a usb-port.
I found the perl-script below but I'd like to accomplish the same with
python:
I guess I have to use the module serial but I don't know how I should
set the serial parameters so they are the same as in the perl-script.
Could someone supply me the command for setting the serial-parameters
correctly
in Python?
thanks
Jean
#!/usr/bin/perl
use strict;
use warnings;
use Device::SerialPort;
die(Usage: $0 /dev/ttyS0\n) unless $#ARGV == 0;
my ($devicepath) = @ARGV;
my $port = new Device::SerialPort($devicepath);
die Couldn't open serial port if ! defined $port;
$port-baudrate(2400);
$port-databits(8);
$port-parity(none);
$port-stopbits(1);
$port-handshake(none);
$port-rts_active(0);
$port-dtr_active(1);
#$port-read_char_time(5); # wait 5ms per character
$port-read_const_time(200); # 0.2 second per unfulfilled read
call
$| = 1; # autoflush STDOUT
while(1) {
my ($nin, $in) = $port-read(255);
print $in;
}
$port-close;
--
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pySerial question, setting certain serial parameters [newbie]
I need to set the following options I found in a Perl-script in Python for serial communication with a device (a voltmeter): $port-handshake(none); $port-rts_active(0); $port-dtr_active(1); I have thus far the following statements but I think it does not set the above parameters correctly: import serial voltport='/dev/ttyUSB2' ser2 = serial.Serial(voltport, 2400, 8, serial.PARITY_NONE, 1,timeout=15) thanks Jean -- http://mail.python.org/mailman/listinfo/python-list
how to read serial stream of data [newbie]
I'd like to read in a stream of data which looks like this: the device sends out a byte-string of 11 bytes roughly every second: B0B0B0B0B03131B0B50D8A B0B0B0B0B03131B0B50D8A B0B0B031B63131B0310D8A B0B034B3323432B3310D8A B0B03237B53432B3310D8A . . . As you see every string is ended by 0D8A How can this be accomplished in Python? thanks Jean -- http://mail.python.org/mailman/listinfo/python-list
