Re: [Tutor] roman to arabic
On 27/02/12 14:41, Cranky Frankie wrote: A quote worth mentioning here is: If you need more than 3 levels of indentation, you're screwed I've always wondered about this quote. I'm thinking it means you might want to have functions or subroutines, depending on the language, to do big chunks of logic, That's one option. The OP also had the option of using a lookup table(dictionary) or just using elifs instead of nested ifs. Often a different algorithm helps. Also functional programming (ie. not just procedural!) can reduce the numbers of indentation levels. (See the FP topic in my tutor for some examples of this.) Simple hiding of indentation levels inside a function is kind of the last resort in reducing indentation levels. Generally deep indentation reveals problems in the basic algorithm and/or data structures. offers almost unlimited indentation, so it's up to the programmer to not use it? Correct, this is a program design decision not a language feature. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] roman to arabic
Hi, I wrote a little program that does the conversion (I won't post it because it would be a spoiler for the OP). The one thing I don't know, though, is how to formalise that it is not allowed to write something like X, but instead just II. Or not DM but simply D. The rule is to write it the shortest possible way. Am I wrong or is it really not trivial at all to write an error class for such lengthy roman numerals? Regards, Albert-Jan ~~ All right, but apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, a fresh water system, and public health, what have the Romans ever done for us? ~~ From: Alan Gauld alan.ga...@btinternet.com To: tutor@python.org Sent: Monday, February 27, 2012 4:37 PM Subject: Re: [Tutor] roman to arabic On 27/02/12 14:41, Cranky Frankie wrote: A quote worth mentioning here is: If you need more than 3 levels of indentation, you're screwed I've always wondered about this quote. I'm thinking it means you might want to have functions or subroutines, depending on the language, to do big chunks of logic, That's one option. The OP also had the option of using a lookup table(dictionary) or just using elifs instead of nested ifs. Often a different algorithm helps. Also functional programming (ie. not just procedural!) can reduce the numbers of indentation levels. (See the FP topic in my tutor for some examples of this.) Simple hiding of indentation levels inside a function is kind of the last resort in reducing indentation levels. Generally deep indentation reveals problems in the basic algorithm and/or data structures. offers almost unlimited indentation, so it's up to the programmer to not use it? Correct, this is a program design decision not a language feature. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] roman to arabic
On 27/02/12 16:28, Albert-Jan Roskam wrote: possible way. Am I wrong or is it really not trivial at all to write an error class for such lengthy roman numerals? Its non trivial, you need something like a state machine to detect valid transitions as you read each character. Alan G. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] roman to arabic
I wrote a little program that does the conversion (I won't post it because it would be a spoiler for the OP). The one thing I don't know, though, is how to formalise that it is not allowed to write something like X, but instead just II. Or not DM but simply D. The rule is to write it the shortest possible way. Am I wrong or is it really not trivial at all to write an error class for such lengthy roman numerals? Mark Pilgrim wrote whole sections on Roman numerals in his Dive Into Python tutorial. While the numerals pop up in various examples throughout the chapters of the tutorial, for this, the tutorial on unit testing may proof helpful: http://www.diveintopython.net/unit_testing/romantest.html Somewhere in that example, there's unit testing code just for examples as above. From the unit test, follow the tutorial into chapter 14 to see how it's done. Hope that helps, Evert Regards, Albert-Jan ~~ All right, but apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, a fresh water system, and public health, what have the Romans ever done for us? ~~ From: Alan Gauld alan.ga...@btinternet.com To: tutor@python.org Sent: Monday, February 27, 2012 4:37 PM Subject: Re: [Tutor] roman to arabic On 27/02/12 14:41, Cranky Frankie wrote: A quote worth mentioning here is: If you need more than 3 levels of indentation, you're screwed I've always wondered about this quote. I'm thinking it means you might want to have functions or subroutines, depending on the language, to do big chunks of logic, That's one option. The OP also had the option of using a lookup table(dictionary) or just using elifs instead of nested ifs. Often a different algorithm helps. Also functional programming (ie. not just procedural!) can reduce the numbers of indentation levels. (See the FP topic in my tutor for some examples of this.) Simple hiding of indentation levels inside a function is kind of the last resort in reducing indentation levels. Generally deep indentation reveals problems in the basic algorithm and/or data structures. offers almost unlimited indentation, so it's up to the programmer to not use it? Correct, this is a program design decision not a language feature. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] roman to arabic
Ah, nice! Thank you! Sseeing the formal rules makes it easier: http://www.diveintopython.net/unit_testing/stage_5.html A regex is used to test whether the roman numeral is valid. Very elegant! Regards, Albert-Jan ~~ All right, but apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, a fresh water system, and public health, what have the Romans ever done for us? ~~ From: Evert Rol evert@gmail.com To: Albert-Jan Roskam fo...@yahoo.com Cc: Python Tutor tutor@python.org Sent: Monday, February 27, 2012 5:42 PM Subject: Re: [Tutor] roman to arabic I wrote a little program that does the conversion (I won't post it because it would be a spoiler for the OP). The one thing I don't know, though, is how to formalise that it is not allowed to write something like X, but instead just II. Or not DM but simply D. The rule is to write it the shortest possible way. Am I wrong or is it really not trivial at all to write an error class for such lengthy roman numerals? Mark Pilgrim wrote whole sections on Roman numerals in his Dive Into Python tutorial. While the numerals pop up in various examples throughout the chapters of the tutorial, for this, the tutorial on unit testing may proof helpful: http://www.diveintopython.net/unit_testing/romantest.html Somewhere in that example, there's unit testing code just for examples as above. From the unit test, follow the tutorial into chapter 14 to see how it's done. Hope that helps, Evert Regards, Albert-Jan ~~ All right, but apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, a fresh water system, and public health, what have the Romans ever done for us? ~~ From: Alan Gauld alan.ga...@btinternet.com To: tutor@python.org Sent: Monday, February 27, 2012 4:37 PM Subject: Re: [Tutor] roman to arabic On 27/02/12 14:41, Cranky Frankie wrote: A quote worth mentioning here is: If you need more than 3 levels of indentation, you're screwed I've always wondered about this quote. I'm thinking it means you might want to have functions or subroutines, depending on the language, to do big chunks of logic, That's one option. The OP also had the option of using a lookup table(dictionary) or just using elifs instead of nested ifs. Often a different algorithm helps. Also functional programming (ie. not just procedural!) can reduce the numbers of indentation levels. (See the FP topic in my tutor for some examples of this.) Simple hiding of indentation levels inside a function is kind of the last resort in reducing indentation levels. Generally deep indentation reveals problems in the basic algorithm and/or data structures. offers almost unlimited indentation, so it's up to the programmer to not use it? Correct, this is a program design decision not a language feature. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] roman to arabic
On 26/02/2012 23:29, Sukhpreet Sdhu wrote: Hi I just wrote python code to convert roman to arabic numerals, but its not working. Can you just check where the problem is and way to correct that. So here is my python code import string print Welcome to the numeric conversion program print Please enter command data=raw_input() now = 0 previous = 0 total = 0 if data == r: print Enter roman numeric to convert in arabic roman_numeric=string.swapcase(raw_input(Enter the Roman Numeral to convert to arabic)) if roman_numeric == (M or D or L or C or L or X or V or I): Length = len(roman_numeric) - 1 i = roman_numeric[Length] if i == M: now = 1000 if i == D: now = 500 if i == C: now = 100 if i == L: now = 50 if i == X: now = 10 if i == V: now = 5 if i == I: now = 1 acc = now if (previous= now): total += acc-prvious print The total is,total if (previous= now): total += acc-prevous print The total is,total else : if data == a : print Arabic number to convert thanks sukhpreet sidhu ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor I'm sorry but the code is so badly formatted via Thunderbird that it's pretty much impossible to work out what you intend. Try resending with the code correctly formatted. Also put print statements into the code so that you can follow the flow and see what it's doing, then you'll be able to make some progress yourself. -- Cheers. Mark Lawrence. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] roman to arabic
Hi , On 26 February 2012 23:29, Sukhpreet Sdhu sukhpreet2294si...@ymail.com wrote: Hi I just wrote python code to convert roman to arabic numerals, but its not working. How exactly is it not working? Please don't make us guess or work more than neccesary trying to help you... Can you just check where the problem is and way to correct that. So here is my python code import string print Welcome to the numeric conversion program print Please enter command data=raw_input() now = 0 previous = 0 total = 0 if data == r: print Enter roman numeric to convert in arabic roman_numeric=string.swapcase(raw_input(Enter the Roman Numeral to convert to arabic)) if roman_numeric == (M or D or L or C or L or X or V or I): Length = len(roman_numeric) - 1 i = roman_numeric[Length] if i == M: now = 1000 if i == D: now = 500 if i == C: now = 100 if i == L: now = 50 if i == X: now = 10 if i == V: now = 5 if i == I: now = 1 acc = now if (previous = now): total += acc-prvious print The total is,total if (previous = now): total += acc-prevous print The total is,total else : if data == a : print Arabic number to convert thanks sukhpreet sidhu Is your code really indented like that? A quote worth mentioning here is: If you need more than 3 levels of indentation, you're screwed anyway, and should fix your program. -- Linus Torvalds Now he was writing w.r.t. C/C++ but the principle holds for Python also in general -- very highly nested levels of indentation are indicative of some kind of program problem, and will likely cause you to conceptually lose control of what the code's supposed to be doing. Can you please explain in english (pseudocode) your algorithm for converting a roman numeral string to arabic numbers, with a more direct explanation of what you've tried and how your solution is not working from what you're expecting. Then we'll be able to help you better and will not be left having to guess at how All that said, apart from the indentation weirdness, a few more offhand observations: I can see 3 different spellings for previous in the code, which will obviously cause problems. The logic to deal with smaller numbers preceding larger numbers seem broken (though I've not looked too closely). The conditions both include equality (= and =) which is likely wrong, the indentation is wrong and both conditions seem to be doing the same thing, which must likewise be wrong. (You'd expect there to be some difference in handling the case when the previous number is smaller that the current number vs when it's larger...) HTH, Walter ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] roman to arabic
On 26/02/12 23:29, Sukhpreet Sdhu wrote:
import string
Are you using a very old versioon opf python?
If not you should not use string.
The built in string methods can do everything you
want without resorting to string.
print Welcome to the numeric conversion program
print Please enter command
data=raw_input()
now = 0
previous = 0
total = 0
if data == r:
print Enter roman numeric to convert in arabic
roman_numeric=string.swapcase(raw_input(Enter the Roman Numeral to convert to
arabic))
Are you sure you want swapcase()? I'd have thought uppercase()
would be more effective given the tests below.
Using built in methods that line becomes:
roman_numeric=raw_input(Enter the Roman Numeral to convert to
arabic).uppercase()
if roman_numeric == (M or D or L or C or L or X or V or I):
This is just wrong!
The parenthesised list will evaluate to True so you are testing if the
variable is True, which it will be if not empty.
You want:
if roman_numeric in (M,D,L,C,L,X,V,I):
Length = len(roman_numeric) - 1
If the variable is one of the items in your list it is only 1 char long
so you re setting Length to zero. Is that what you want?
i = roman_numeric[Length]
If you really want to extract the last digit use a -1 index.
In which case you dshould do the same for the check on valid values...
if i == M:
now = 1000
if i == D:
now = 500
Are you sure you want this structure?
It would look a lot neater using elif
if i == M:
now = 1000
elif i == D:
now = 500
elif i == C:
now = 100
But better still would be to use a dictionary:
values = { 'I':1, 'V':5, 'X':10,...'D':500, 'M':1000 }
now = values[i]
acc = now
if (previous= now):
total += acc-prvious
spelling error in prvious
print The total is,total
if (previous= now):
total += acc-prevous
print The total is,total
else :
This else doesn't line up with any if.
if data == a :
else:
if cond:
could just be
elif cond:
HTH,
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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Re: [Tutor] roman to arabic
On 2/26/2012 6:29 PM, Sukhpreet Sdhu wrote: Hi I just wrote python code to convert roman to arabic numerals [snip] Yuk what a mess. May I suggest you start with a much simpler program, which is to take a roman number between 1 and 3 (just i's) and convert that. First describe how you'd convert the number by hand. Then convert that process to Python. Test the program. Fix any problems. Report back to us success or a problem you don't know how to address. Tell us exactly what went wrong. (e.g. I entered iii expecting 3 and got 17 or if you get a traceback post it. For example when I run your program I get: Traceback ( File interactive input, line 12 if roman_numeric == (M or D or L or C or L or X or V or I): ^ IndentationError: unindent does not match any outer indentation level Then add v (now the number is between 1 and 8). You will come up with a completely different program! And it will be the correct one. Also provide meaningful prompts. print Please enter command If I was running your program and saw that I'd have to give up since I have no idea what is expected. print Please enter command - r for roman-arabic would be much better. -- Bob Gailer 919-636-4239 Chapel Hill NC ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
