# Evaluating a mathematical expression in a string

In this tutorial, we will learn to evaluate a mathematical expression in a string which we can perform using an eval built -in function in a different way that we will discuss here.

#### Mathematical Expression

At times we get the input as a string wherein string there is an expression in such cases we have to extract the mathematical expression as it is and perform the actions which are required so for the same there is a build function that can be used to extract the mathematical expressions from String.

For example, look at the example given below where we have used the same in built function on an expression:

```expression = "2 + 3 * 4 - 6"
result = eval( expression)
print( result)
```

In this, we have simply given all the numbers which we can say direct evaluation but it is smart enough to detect the variable if any given in the expression and perform the mathematical expression for the same following the example given below.

```x = 2
y = 3
expression = "x + y * 4 - 6"
result = eval( expression)
print( result)
```

Here we have given the expression in the form of a String which includes variables, numerical values, and operators which we have to perform.

And even we can use it for input() also and get the solution solved as it has the ability to detect how we can perform and get it done by extracting the values, variables, and operators which we do not need to specify before as these all are pre-defined, For the same the example is given below:

```eval(input(" Enter a math expression: "))
Enter a math expression: 15 * 2
>>> 30
eval(input(" Enter a math expression: "))
Enter a math expression: 5 + 8
13```

Above all eval() function has a role in minimizing the security issues as it allows you to dynamically execute arbitrarily to the python code. As is can be used for evaluating the code given by the user at the time of entering it for input by the user or you.

It also has a number of other functions or properties that makes it a powerful function that we can always use to make the coding easy, and safe and perform complex problems in simple ways and get it done.

To learn more about eval() build in function of python at Use of eval() for getting the expressions out of string and evaluating it asper is given, mathematical rules.

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