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# Python erf() Function | Math.erf() in Python Example

Python erf() is an inbuilt method that is defined under the math module, which is used to find the error function at x if x is the parameter passed. For example if x is passed as a parameter in erf function (erf(x)) it returns error function. We can use a math module by importing it.

## Python erf()

Python math.erf() method will return the error at x. The error function is also known as gauss error function, and the function throws an error if any non-number is passed as a parameter.

### Syntax

```math.erf(var)
```

Here var is the variable of which error function we have to find.

### Parameters

It takes one argument var, which takes values of numeric datatype and throws TypeError if an argument is of any other data type is passed.

### Return Value

It returns the error function value of the number in the float datatype.

See the following sample code.

```import math

var = 0.6
print(math.erf(var))
```

### Example programs on erf() method in Python

#### Example 1: Write a program to show the working of the erf() method in Python.

```import math
a1 = 0.3
b1 = 0.9
c1 = 0.7
d1 = 0.2

print("Value for parameter ", a1, " is ", math.erf(a1))
print("Value for parameter ", b1, " is ", math.erf(b1))
print("Value for parameter ", c1, " is ", math.erf(c1))
print("Value for parameter ", d1, " is ", math.erf(d1))
```

#### Output

```Value for parameter  0.3  is  0.3286267594591274
Value for parameter  0.9  is  0.796908212422832
Value for parameter  0.7  is  0.6778011938374183
Value for parameter  0.2  is  0.22270258921047847
```

In this code example, we have seen that by passing a vaild parameter, which is different for different examples, we get the desired erf() method solution, which is the error function value.

#### Example 2: Write a program to pass the value out of range from the erf() function and display the output.

See the following code.

```import math

x = 'b'
print(math.erf(x))
```

#### Output

```TypeError: must be real number, not str
```

In this example, we’ve seen that by passing a parameter which is not of number type, the function throws an error.