Sharing a script: solve arbitrary blocks of text as math.

paultopia

A common task I have: I want to write down some numbers or a simple formula of some kind, and then go ahead and do something with the numbers or solve a simple equation with them. Examples: writing down how much I paid for each bill in a note or drafts, then summing them; working out a simple algebra equation for something like a mildly complicated tax/tip situation and then solving it.

There are lots of calculators in the built-in Pythonista examples, but none which quite met my needs for dealing with pre-written text. There are also special-purpose apps for things like ticker-tape calculators, but I don't think any of them do algebra, and, besides, why pay for a separate app when pythonista is right there plus has the full power of sympy available?

So I wrote my own little script. Takes share sheet or clipboard input string. If it's just a list of numbers, sums them. If there are arithmetic operators, evaluates the expression. If it's a simple one-variable expression, assumes it's an equation with the other side zero and feeds it to sympy to solve. If it's a one-variable equation, back to sympy. Should handle most basic day-to-day ticker-tape math needs, in only 75-ish lines of actual code.

https://gist.github.com/paultopia/16e69f9f72ad0a5000fa5b4575ddeee2

mikael

@paultopia, this is really fun! And useful. I am tempted to build a little machinery around this, maybe a scroll view that shows the latest calculations, an entry field and two buttons, one that calculates with what’s given, and another that starts from the previous result... Or something like that.

paultopia

@mikael That would be cool! I can stick this into a proper repo if you want ...

mikael

@paultopia, as a first thing, I made an Apple shortcut to enter the text, but that is not ideal as there does not seem to be a way to force the keyboard to numbers mode in Shortcuts.

Then I made Siri take dictation. This needed a lot of language-specific tweaking to convert the operations (e.g. Siri likes to use '×' and '÷') and small numbers (Siri prefers ”four” to ”4” in many cases). And all of these in Finnish, of course.

But now the kids are astonished when I solve equations by speaking to Siri. 👍🏻😁

cvp

@mikael said:

I made an Apple shortcut to enter the text

Why do you want to enter the numbers in a shortcut and not in Pythonista which could allow a user keyboard with only digits?

mikael

@cvp, actually started from the dictation, then when that was initially quite unreliable, checked out what the typing experience was like.

After checking the out of the box capabilities, I am now moving full hog to Pythonista.

First thing I noted was that iOS is really missing a native keyboard option that would be spot on for a calculator.

cvp

@mikael easy with this

mikael

@cvp, very true. Would need to add a few mathematical operations, and then it would be perfect. Does the user have to give permission if you use this?

mikael

@paultopia, to make sure I understand what is happening, and to add a few features like result precision and tokenization, I re-implemented your code as a class. It is here, intended to be used like this:

    >>> Kalkylation("1 2\\n3")
    Input: 1 + 2 + 3
    Symbolic result: 6
    Numeric result: 6.00
    
    >>> k = Kalkylation("1 = 2+x")
    >>> k
    Input: 1 = 2 + x
    Symbolic result: -1
    Numeric result: -1.00
    
    >>> k.tokens
    ['1', '=', '2', '+', 'x']
    
    >>> Kalkylation.result_decimals = '.000001'
    
    >>> Kalkylation("1+23 =3+x**2")
    Input: 1 + 23 = 3 + x ** 2
    Symbolic result: -sqrt(21), sqrt(21)
    Numeric result: -4.582576, 4.582576

cvp

@mikael said:

Does the user have to give permission if you use this?

Sorry if I don't understand your question but my code is available here

mikael

@cvp, I meant that this looks like an in-app keyboard, which is excellent, as cross-app custom keyboards need to ask for permission.

cvp

@mikael ok, sorry, in-app

cvp

@mikael error

NameError: name 'ROUND_HALF_EVEN' is not defined

from decimal import Decimal, ROUND_HALF_EVEN

mikael

@cvp, curious, works for me. Restart Pythonista?

cvp

@mikael As this is a "from decimal", it seems normal to import it, isn't it?

from decimal import Decimal, ROUND_HALF_EVEN

Has solved

cvp

Copy my SetTextFieldPad from GitHub and place this code after @mikael 's module


import ui
from SetTextFieldPad import SetTextFieldPad

def my_action(sender):
    sender.TextField.close()

 
tf = ui.TextField()
#pad = [{'key':'','title'=:'','icon':''}]
pad = [{'key':'1'},{'key':'2'},{'key':'3'},
        {'key':'back space','icon':'typb:Delete'},
        {'key':'new row'},
        {'key':'4'},{'key':'5'},{'key':'6'},
        {'key':'delete','icon':'emj:Multiplication_X'},
        {'key':'new row'},
        {'key':'7'},{'key':'8'},{'key':'9'},
        {'key':'x'},
        {'key':'new row'},
        {'key':'+'},{'key':'='},
        {'key':'⏎', 'action':my_action},
        {'key':'new row'},
        {'key':'nul'},{'key':'0'}]
SetTextFieldPad(tf,pad=pad)
tf.text = ''
tf.width = 400
tf.present('sheet')
tf.begin_editing()
tf.wait_modal()
k = Kalkylation(tf.text)
print(k)

And you will get

mikael

@cvp said:

from decimal import Decimal, ROUND_HALF_EVEN

My turn to misunderstand, sorry. I thought you had already added this, and it still wasn’t finding it.