[Tutor] Python, VB math simple problem

[Kent Johnson]

Mr X wrote:
> 
> 
> Hi looking for help with what should be a fairly simple Python problem, 
> relating to VB inter-operability.
> Got a great response from a fellow named Matt at help at python.org, 
> pointed me in some good directions - some areas, concerns still foggy 
> on, the below thread is included.... any feedback on this simple dilemma
> would be very appreciated.

You can use py2exe to make an executable from a python program. Or the 
VB program could invoke a command line like "python prog.py data.txt" 
without needing to use py2exe. You can also write COM servers in Python.

Kent

> 
> Thanks,
> 
> D
> 
> thread follows below;
> 
> ------------------------------------
> 
> To: help at python.org
> Subject: Problem with Python math functions and VB
> Date: 3/30/2006 9:39:28 PM
> Download Message Display Headers Printer Friendly
> Previous | Next
> 
> Wondering if you might either know how to solve the following.
> 
> I've a background in Visual Basic, and am using an old version, 4.0, it 
> compiles to a smaller executable which I prefer. I find myself in an odd 
> situation, needing a very simple yet powerful capability of Python for a 
> VB app
> Im working on.
> 
> Simply, a large 300 digit number is divided by a smaller number ranging 
> from 1 to 3 digits. I.e;
> 
> This large 300 digit number is generated as a string from the VB app, 
> and I want to input this somehow
> from the VB app directly to Python for simple math operations.
> 
> Where; x = 300 digit number, y = divisor ( say '37')
> 
> 
> x / 37
> 
> I want to divide x by y but I want the remainder of this division to at 
> least 3 or 4 decimal places, so my Python script at the command line;
> 
> x %y /y. = z
> 
> So now I want to take the resultant, the full number plus its remainder, 
> and I want to round this number up
> to the next highest number and divide it by the same constant;
> 
> z rounded up to next highest number (never the lowest)
> 
> so
> 
> z /y = z Long
> 
> Remove the 'L' at the end, round up the last digit of z = Z
> 
> Then;
> 
> Z %y /y. = a
> 
> Then I want the last five digits of z (not Z) and a truncated at the 
> end, so the last digit before
> the decimal point and the four digits past the decimal point printed to 
> a text file.
> 
> I want to be able to open the text file with the VB app and use this 
> data as inputs.
> ==========
> 
> Ok, so here is my dilemma, I know VERY litle about Python and a fair bit 
> about VB.
> 
> Ideally, I'd love to be able to simply have some extremely small 
> executable that just accepts inputs
> does the calculations above and then spits out the outputs. If it were 
> possible to write some
> simple lines of math code in Python and then compile these scripts in 
> Python to a Windows
> compatible executable,that would be fantastic.
> 
> If I could simply have my VB app, 'call' the name of the tiny Python 
> executable, and then the Python executable
> just automatically looked for a named text file (created by the VB app) 
> and extracted the 300 digit number from this, then performed the calcs, 
> then spit this data out as a new text file name it created, which I 
> could then use the VB app to open and read from, THAT would be ideal.
> 
> However, I don't know if Python can compile scripts to an exe? If it can 
> how could I find out how to do this?
> 
> If it doesn't, how could I get VB to directly pass commands to the 
> Python command line and then automatically
> extract the outputs? Shelling out from VB to Python would be tough to 
> the command line I think, since the Python command line uses the 'Edit / 
> Mark, Paste' approach to inserting, copy inputs, outputs and this would 
> be virtually untenable, as far as I can tell to automate in a VB shell 
> out routine.
> 
> So basically, how the heck can I access Pythons ability to perform 
> simple calculations on very large numbers, easily, from within VB 4.0 ? 
> There must be a way, it seems like such a simple think to do, especially 
> since the actual math operations are so simple, straight forward, and 
> would never change.....
> 
> Any ideas?
> 
> 
> 
> ------
> Matthew, thanks for your response.
> 
> <-----Original Message----->
>  >From: Matthew Dixon Cowles
>  >Sent: 3/31/2006 9:41:18 AM
>  >To: durango at mail2world.com
>  >Cc: help at python.org
>  >Subject: Re: [Python-Help] Problem with Python math functions and VB
> 
>  >I'm sure that there's a way to do that, but I'm not familiar with
>  >Visual Basic and I don't know what inter-process communication
>  >facilities it offers.
> 
> Is there a person or group you might direct me to that has worked with this
> inter-process communication between VB and Python?
> 
>  >I don't think that Python is going to be able to do that for you out
>  >of the box. Hundreds of digits of floating-point precision is a lot.
> 
> Could you explain that a bit more, sorry Im not sure what you mean
> by 'out of the box' ? If I run the Python command line screen in windows
> and manually type out a very large number, say 180 digits; where 'X' = 
> very large number;
> 
> X %37 /37.
> 
> returns what Im after, value wise..... but of course I don't want to do 
> this manually each time
> for every dividend.
> 
>  >You might find that one of the Python modules that let you use an
>  >extended-precision library would do what you want. GMPY is one:
> 
>  >http://gmpy.sourceforge.net/
> 
> Hey, thats interesting, wonder if these modules can be operated on with 
> VB.....
> 
>  >> So now I want to take the resultant, the full number plus its
>  >> remainder, and I want to round this number up
>  >> to the next highest number and divide it by the same constant;
>  >
>  >That's easy enough.
>  >
>  >> I want to be able to open the text file with the VB app and use this
>  >> data as inputs.
>  >
>  >Python can write to a file without any trouble, so it that form of
>  >inter-process communication suits you, you shouldn't have much
>  >trouble. I assume that Visual Basic has an easy way to start a
>  >program and supply it with arguments, so you could have your Python
>  >program get its inputs from sys.argv.
> 
> What is sys.argv ? Thats really good news. In fact, all I really need 
> for the moment is
> a python executable that;
> 
> ================
> PYTHON ALGORITHM ABSTRACT
> 
> a) opens a text file
> b) reads a string from the file, which is a very large number
> c) performs simple arithmetic operations;
> 
> X %37 /37. = y (four digit remainder after decimal point)
> X /37 = w (quotient as long, the resulting output is stored as a 
> variable, the 'L' suffix tagged on the end of this resultant then gets 
> removed.
> then the last digit in the quotient resultant string is increased in 
> value by one, rounded upwards = 'Z'
> 
> then
> 
> Z %37 /37. = a
> 
> then, y and a are printed to a text file with hard returns between them. 
> Thats it, thats all I need to do.
> ===================
>  >Alas, it's not going to be extremely small. There isn't a compiler
>  >from Python to machine code. Py2exe will bundle a Python program,
>  >with everything that it needs to run, into a single executable
>  >archive. But the archive isn't small. Py2exe is at:
>  >
>  >http://www.py2exe.org/
> 
> the most important thing is the functionality, I'll sacrifice size if I 
> have to. My guess is this should work based on your comments, because
> perhaps all I really have to do is have VB dump out the value of the 
> Very large number, `180 to 300 digits or so', to a text file, which then
> becomes the input data for the Python executable, and then if I simply 
> call the name of the Python executable from VB as an instance,
> then the Python App runs, spits out the data as a new text file, then 
> the VB app goes and opens the new text file and reads in the values,
> and voila! There it is. I'm pretty sure I can call the Python app from 
> VB....... the alternative to all this would be to try and feed Python 
> scripts
> directly to Python from VB, which I have NO idea how to do or where to 
> begin.... and am guessing would be much more messy...
> 
> I haven't programmed in Python, how would the "PYTHON ALGORITHM 
> ABSTRACT" I describe above look like, code wise?
> Is this fairly easy for you to describe?
> 
>  >It may be that Python isn't the best solution for you here. Are there
>  >extended-precision libraries for Visual Basic?
> 
> Alas, none that I know of that are reliable and not incredibly 
> expensive, been looking for years, plus Im hooped because I have to work
> with VB 4.0 instead of 6 +, guh....
> 
>  >Regards,
>  >Matt
> 
> Matt..... good name, why do I always seem to get along with Matts, you 
> people keep popping up in my life and its always a blast!
> 
> Best regards,
> 
> D
> 
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