I want to do a basic calculator in Python3 but I have only seen that it works using methods and conditions.
But is it possible that entering the whole operation in an Iput, obtain the same result?
Example:
input("Ingresa tu operacion: )
2*5
10
Something more or less so just leave a message asking for the operation and automatically do it.
I hope to be clear
what you can do is check each character to identify the operator. I made my own version of the program, check it out to see if it works. (EYE: It only works with an operand)
class Operador():
NOOP = 0
SUMA = 1
RESTA = 2
MULTIPLICACION = 3
DIVISION = 4
entrada = input()
tamano = len(entrada)
operador = Operador.NOOP
i = 0
while operador == Operador.NOOP or i >= tamano:
if entrada[i] == '+':
operador = Operador.SUMA
elif entrada[i] == '-':
operador = Operador.RESTA
elif entrada[i] == '*':
operador = Operador.MULTIPLICACION
elif entrada[i] == '/':
operador = Operador.DIVISION
i += 1
if(operador != Operador.NOOP):
argumento1 = float(entrada[0:i-1])
argumento2 = float(entrada[i:])
if operador == Operador.SUMA:
print (argumento1+argumento2)
elif operador == Operador.RESTA:
print (argumento1-argumento2)
elif operador == Operador.MULTIPLICACION:
print (argumento1*argumento2)
elif operador == Operador.DIVISION:
print (argumento1/argumento2)
else:
print ("No se identifico el operador")
Evaluating an expression as you mention is relatively simple, as NaCI has already mentioned, you can use eval which is base functionality:
from math import sqrt
valor = eval("2*3")
print(valor)
> 6
valor = eval("sqrt(4)")
print(valor)
> 2.0
But eval() does not evaluate arithmetic operations evaluates Python code, therefore it is a dangerous routine, if you are going to offer it to a user, you are opening the possibility of executing any code.
A more limited solution is to use some mathematical evaluator, there are several. Simply by way of example I can suggest py-expression-eval
The installation, in the usual way: pip install py_expression_eval
To execute it:
from py_expression_eval import Parser
parser = Parser()
valor = parser.parse('2 * 3').evaluate({})
print(valor)
Verify in PyPI , there are simpler evaluators and others more complex, the idea is always the same, offer a code evaluation more limited to the mathematical and minimize the problems due to the execution of undesired code.