Calculate Expression

A simple calculator dealing with expressions in string type ,using stack data structure.

Features

• You can custom each operator's priority and behavior.
• Expressions both with and without algebras are supported.

Caution

• spaces in input expressions will be removed while processing.
• each expression will be converted into (expression) before processing to avoid empty stack problems.

Installation

$ pip install calculate-expression

* since using f-string for formating ,could only be installed on python3.6+

Usage

initialize a standard calculator: (optional parameters "rule" & "regularization")

from calculate_expression import ce
standard = ce.Calculator()

You can custom your own operator sets ,default ones like this:

# "operator":(priority,'behavior')
# behavior is string type ,thus we can easily check its logic
# we will use eval() to convert it into function later
rules = { '+' : (0 ,'lambda x,y:x+y') ,
         '-' : (0 ,'lambda x,y:x-y') ,
         '*' : (1 ,'lambda x,y:x*y') ,
         '/' : (1 ,'lambda x,y:x/y') , 
         '^' : (2 ,'lambda x,y:x**y') }
standard = ce.Calculator(rules)

* once new operator is added ,regularization function may need to be modified commensurately.

* default regularization function: lambda x:x.replace("**","^").replace('\\','/')

You can check operate rules and regularfunction like this , Thus you can easily modify it.

> standard.printinfo()
> 
> defalut_regularization_function = lambda x:x.replace('**','^').replace('\\','/')
> 
> rules = { '+' : (0, 'lambda x,y:x+y') ,
>           '-' : (0, 'lambda x,y:x-y') ,
>           '*' : (1, 'lambda x,y:x*y') ,
>           '/' : (1, 'lambda x,y:x/y') ,
>           '^' : (2, 'lambda x,y:x**y') }
>

Try a simple calculate

> print( standard.calculate('1 + 2 * 3') )
> 7

Algebra is supported

> print( standard.calculate('a + b * c' ,a = 1 ,b = 2 ,c = 3) )
> 7

Once introduced ,algebras will be stored in whose object's attribute as a dictionary , It will remain until it's updated.

> print( standard.calculate('' ,a = 1 ,b = 2 ,c = 3 ,d = 4 ,e = 1.6) ) # update params only 
> None
> print( standard.calculate('d ** 4 / e') )
> 160
> print( standard.calculate('d ** 4 / e' ,e = 0.1625) )
> 1575.3846153846152

Have fun.