Re: [Tutor] Hi there, have a question for a side project in physics.....
On Mon, Dec 25, 2017 at 09:45:35AM +, Alan Gauld via Tutor wrote: > On 25/12/17 09:08, Siddharth Sehgal wrote: > > >physics masters student. I am trying to use the Sellmeier Equation > > >I originally state them as floats. However such a process apparently > > >cannot be done with "floats" like these. > > It can be done just with a large error (although as a physics > grad you will know how to calculate the error I assume) I don't think the numbers or equation is so ill-conditioned that the error will be "large", or at least not larger than the experimental uncertainty in the coefficients. Floating point maths is tricky, but it isn't *that* tricky. Especially not for "reasonable" sized numbers, with only nine or ten significant figures. This is the huge advantage of IEEE-754 maths using 64-bit floats, as Python does: most of the time, the obvious formula "just works". -- Steve ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Hi there, have a question for a side project in physics.....
On Mon, Dec 25, 2017 at 01:08:13PM +0400, Siddharth Sehgal wrote: > The actual equation is below screen shotted No it isn't -- either you forgot to attach it, or the mailing list removed it. Do you mean this equation? https://en.wikipedia.org/wiki/Sellmeier_equation I suggest you try using Python and compare your results to those from here: http://www.calctool.org/CALC/phys/optics/sellmeier or from some authoritative source of refractive indexes. Here is my simple test, for borosilicate glass BK7 using the values from Wikipedia. Using the website: refractive index at 590 nm = 1.51670 Using Python, I get: 1.516698697993053 Here is my code. Feel free to use it for any purpose, no credit required (except as needed to meet any academic obligations you may have about collaboration and/or plagiarism). import math def sellmeier(lambd, B1, B2, B3, C1, C2, C3): return 1 + B1*f(lambd, C1) + B2*f(lambd, C2) + B3*f(lambd, C3) def f(x, y): x2 = x**2 return x2/(x2 - y) # Coefficients for BK7 (borosilicate crown glass) result = sellmeier(0.590, # 590nm == 0.590µm 1.03961212, 0.231792344, 1.01046945, 6.00069867e-3, 2.00179144e-2, 103.560653) print(math.sqrt(result)) -- Steve ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Hi there, have a question for a side project in physics.....
On Mon, Dec 25, 2017 at 01:08:13PM +0400, Siddharth Sehgal wrote: > Hi there > > > I am a novice python user and am a physics masters student. I am > trying to use the Sellmeier Equation to calculate a refractive index. > The coefficients of this equation are decimals to a large number of > sig figs ( i.e B1 = 1.03961212, B2 = 0.231792344, C1 = 6.00069867×10−3 That's not really a lot of significant figures. Python floats are C 64-bit doubles, so they can represent about 15 or 16 significant figures. The numbers you show are only 9 or 10. > ... and so on) in the sellmeier formula there is a lot of fractions, > multiplication and squaring of these numbers. I originally state them > as floats. However such a process apparently cannot be done with > "floats" like these. What makes you think that you cannot use floats for this? Of course floating point maths on computers is not the same as real arithmetic of the Real numbers in mathematics class, and you may need to carefully consider the possible error conditions in your equations, round-off error, and so forth, but in general I would expect that simply using Python as a calculator will be fine for all but the most precise calculations. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Hi there, have a question for a side project in physics.....
On 25/12/17 09:08, Siddharth Sehgal wrote: physics masters student. I am trying to use the Sellmeier Equation I originally state them as floats. However such a process apparently > cannot be done with "floats" like these. It can be done just with a large error (although as a physics grad you will know how to calculate the error I assume) What do i do? PLEASE NEED HELP! There ae several ways and I guess the best will involve using SciPy/numpy features. But since i don't know those I'll suggest the old school way which is to multiply your numbers up until they become integers and take advantage of pythons big int feature. You will need to plug all the multipliers into your formula and work out the final multiplier - but that is just exponent arithmetic so should be doable. Finally adjust your answer by the calculated exponent. As I say there will probably be better solutions in the numpy space and hopefully someone else will tell you about them. The actual equation is below screen shotted This list does not permit non-text attachments - the server throws them away. Alan G. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
[Tutor] Hi there, have a question for a side project in physics.....
Hi there I am a novice python user and am a physics masters student. I am trying to use the Sellmeier Equation to calculate a refractive index. The coefficients of this equation are decimals to a large number of sig figs ( i.e B1 = 1.03961212, B2 = 0.231792344, C1 = 6.00069867×10−3 ... and so on) in the sellmeier formula there is a lot of fractions, multiplication and squaring of these numbers. I originally state them as floats. However such a process apparently cannot be done with "floats" like these. What do i do? PLEASE NEED HELP! The actual equation is below screen shotted Many thanks, I look forward to your response, THIS IS NOT HOMEWORK BY THE WAY, I just want to use this program as it saves a lot of writing on paper. Siddharth Sehgal MSc Student in Physics SUNY - Stony Brook University ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Hi there,
On Sat, Jan 02, 2016 at 02:45:30PM +0200, yehudak . wrote: > I'm trying to write a Python 3.5 program to find how many trailing zeros > are in 100! (factorial of 100). > I downloaded factorial from Math module, but all my efforts to solve the > problem failed. > > I know the mathematical way to solve it (resulting in 24), but I want a > Python solution. Here are the steps needed: http://www.purplemath.com/modules/factzero.htm Try writing some Python code for this, and if you have trouble, show us your code and we'll help. But you have to write it first -- we won't do your homework for you. -- Steve ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Hi there,
On 02/01/16 12:45, yehudak . wrote: > I know the mathematical way to solve it (resulting in 24), but I want a > Python solution. Show us your code. Usually "the mathematical way to do it" works in Python too. Although there will likely be other ways that may sometimes run faster or easier to code. But until we see your code we can't comment on what you are doing. One way to try would be continually dividing by 10 until you get a non-zero remainder. Count the number of divisions necessary. Hint: The divmod() function may help here. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: 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] Hi there,
I'm trying to write a Python 3.5 program to find how many trailing zeros are in 100! (factorial of 100). I downloaded factorial from Math module, but all my efforts to solve the problem failed. I know the mathematical way to solve it (resulting in 24), but I want a Python solution. Thank you. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Hi there :.)
Alan Gauld, 15.03.2010 20:28: wrote (apparently python is slow ?!?). It is all relative. If you want to write fast moving graphics etc then yes, you probably need C++. For anything else you might find Python is fast enough. A good approach tends to be: write it in Python first, benchmark it, find out *if* it's too slow. If so, find out *what* exactly is too slow, optimise that code, benchmark again. Iterate. If there are still parts that are too slow, move the 1-5% of your code that are most time critical into Cython. Benchmark, optimise. Iterate. And only *then*, move on to plain C/C++ if you can really prove with verified benchmarking numbers that you need to. In almost all cases, you don't. In any case, it will safe you all of the hassle of writing the entire code in C/C++, which usually safes you weeks, months or years of developer time, depending on the complexity of your application. Stefan ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Hi there!
Hi! Does anyone of you know where to find all the solutions of Gerard Swinnen Python tutorial exercises In the tutorial we just have the solutions to half of the exercises. Thank you -- Marc-O. Rompré ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Hi there :.)
wrote Just introducing myself to say hiHi! Hi welcome, but please don't include lots of attachments. It blows up people's mailboxes and bandwidth allowances. Better to post them on a website and send a link. I'm very new to programming, ... place to start I found out that python and C++ are the usual starting place Actually there are many: VisualBasic, Lisp/Scheme and Java are all common starting points too. And each has its own merits depending on what you want to do. but when I found out that civilisation and eve are programmed using python (my favorite type of games), that helped make the decision. As good a reason as any! :-) My first aim is to get comfortable with python and move on to C++ (apparently python is slow ?!?). It is all relative. If you want to write fast moving graphics etc then yes, you probably need C++. For anything else you might find Python is fast enough. The problem i'm having with this is with the platform. I want the ball to fall if it goes off the edge but be able to jump when on the platform. it either will fall off the edge but won't jump or it will jump but it won't fall. I don't want to change the way the controls are worked (with the true/ false). test.py is the one file that didn't show up (at least for me) Lots of "demos" but no test.py. It is probably best if you can create the simplest possible example that shows the problem rather than expecting folks to read through half a dozen fairly big files and try to guess what the design looks like etc. (That may have beeen what test.py was!) Try to send some specific code that causes a problem, or at least that you think is causing the problem. Plus any error messages. It would help to tell us which OS and Python version you are using too. HTH, -- Alan Gauld 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] Hi there :.)
On Mon, Mar 15, 2010 at 10:23 AM, wrote: > Hey, > Just introducing myself to say hiHi! > > I'm very new to programming, I got interested in it when I decided to have > a go at html. When looking around for a place to start I found out that > python and C++ are the usual starting place but when I found out that > civilisation and eve are programmed using python (my favorite type of > games), that helped make the decision. so far I've been using Create Your > Own Games with Python (using python 3.1 and pygame) as a guide and been > experimenting making snippets of code. > Welcome to Python and programming! HTML is what got me started on my path, too. Pygame is a great package for making games with. > My first aim is to get comfortable with python and move on to C++ > (apparently python is slow ?!?). My ultimate aim is to create a couple of > ideas that I've had floating around for a while. > Slow is a relative term. If C++ does something 100x faster than python, and python can already do it in .5 seconds you won't notice much difference if you're doing it once. If you're doing 2-d game programming Python is certainly fast for plenty of stuff. Take a look at the games of pyweek: http://www.pyweek.org/ Code is available for all the games so you can take a look at how they program and that might help you with challenges you face. HTH, Wayne ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
