How to Solve and Equation With Inputs in Python

How to solve and equation with inputs in python

The input() function returns a string value: you need to convert to a number using Decimal:

from decimal import Decimal

A = Decimal(input("Enter a number for A: "))
# ... etc

But your user might enter something that isn't a decimal number, so you might want to do some checking:

from decimal import Decimal, InvalidOperation

def get_decimal_input(variableName):
    x = None
    while x is None:
        try:
            x = Decimal(input('Enter a number for ' + variableName + ': '))
        except InvalidOperation:
            print("That's not a number")
    return x

A = get_decimal_input('A')
B = get_decimal_input('B')
C = get_decimal_input('C')
D = get_decimal_input('D')
E = get_decimal_input('E')

print((((A * 10 ** A) ** 2) ** (B * C)) * D ** E)

Python User input equation

Tack för exempel -- that allowed me to determine what you need.

Yes, this is possible. Read in the equation as a string variable, such as

equation = input("Enter your equation here")

Then when you want to find a value for e, use the Python eval method:

e = eval(equation)

Be very careful with this method: eval() is powerful, and very discriminating about what it accepts.

• eval is really
  dangerous
• Security on untrusted
  strings

How to solve a math equation if the input is a string in python?

You can split at the '+' sign numbers=input.split('+'), then remove the '=' form the end, secondNumber=numbers.split('='). Afther that write

 if operator == '+':
   output = numbers[0] + secondNumber[0]
   print(output)

Or just output=eval(input.split('=')[0])

How to get equation from input in python

If ths code is for academic purposes and you don't want to involve third party libraries, the eval() function in Python is built just for this. You can create a function which evaluates a string expression expr for a value x as such:

def func(expr, x):
    return eval(expr)

input_expr = input('Enter an expression in x: ')
val = 5
print(func(input_expr, val))

Input: x*x*x - x*x + 2

Output: 102

eval() treats the string passed to it as a right hand side expression and evaluates it. So, when the user-input string 'x*x*x - x*x + 2' is passed to the function, the statement return eval('x*x*x - x*x + 2') is equivalent to return x*x*x-x*x+2.

Note that this means there must be a variable x in scope, which we handle by wrapping the eval() function in the function eval_expr().

A problem would arise however, if the user input something like y*y*y+y*y-2 as y isn't declared in the scope. If you need to handle such cases, then you would need to write additional code that converts the input string by replacing any alphabetical character in it to x.

It should be noted that eval generally isn't considered safe, and if this code is not for academic purposes and needs to be safe, you should consider using python libraries like numexpr or pyparsing. numexpr should be fairly easy to use and would suffice for your application.

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