In Python, an average function is a way to calculate the average value of a given set of numbers. The average function can be used in a variety of scenarios, from simple calculations of a list of numbers to more complex statistical analyses.

## Methods to Implement Average Function

There are several ways to implement an average function in Python.

### Method 1: Using Built-In sum() and len() Functions

One common method is to use the built-in sum() and len() functions to calculate the sum of the numbers in the list and the number of elements in the list, respectively. Then, divide the sum by the length of the list to get the average. Here is an example of an average function implemented in this way:

def average(numbers): if len(numbers) == 0: return None else: return sum(numbers) / len(numbers) list = [1, 2, 3, 6] print "The average of list is ", round(average(list), 2)

**Output:**

`The average of list is 3.0`

**Explanation:** This average function takes a list of numbers as its input parameter and returns the average of the numbers. The function first checks if the length of the list is 0, and if so, returns None. Otherwise, it calculates the sum of the numbers using the built-in sum() function and divides it by the length of the list to get the average.

### Method 2: Iterating the Loop

Another way to implement an average function is to use a for loop to iterate through the list of numbers and add them up. Here is an example of an average function implemented using a for loop:

def average(numbers): if len(numbers) == 0: return None else: total = 0 for num in numbers: total += num return total / len(numbers) list = [3, 5, 6, 8] print "The average of list is " , average(list)

**Output:**

`The average of list is 5`

**Explanation:** This function also takes a list of numbers as its input parameter and returns the average of the numbers. The function first checks if the length of the list is 0, and if so, returns None. Otherwise, it initializes a variable called total to 0 and uses a for loop to iterate through the list of numbers, adding each number to the total. Finally, the function divides the total by the length of the list to get the average.

### Method 3: Using Built-In mean() Function of Statistics Module

There are also built-in functions in Python’s statistics module for calculating various types of averages, including the mean, median, and mode. Here is an example of using the mean() function from the statistics module to calculate the average of a list of numbers:

import statistics numbers = [1, 2, 3, 4, 5] avg = statistics.mean(numbers) print("The average of list is ",avg)

**Output:**

`The average of list is 3`

**Explanation:**

This code imports the statistics module and creates a list of numbers. It then calls the mean() function from the statistics module, passing in the list of numbers as its input parameter. The mean() function returns the average of the numbers, which is then printed to the console.

### Method 4: Using reduce() and Lambda Functions

We can use the reduce and lambda functions in Python to find the average of a list of numbers. The lambda function is used to compute the sum after looping through the list with the reduce method.

To find the average of a list using reduce and lambda functions in Python, you can follow these steps:

- To use the reduce function, import the “reduce” from the “functools” module.
- Define a list of numbers.
- Use the reduce function with a lambda function that sums the values in the list.
- Divide the sum by the length of the list.

from functools import reduce my_list = [1, 2, 3, 4, 5] average = reduce(lambda x, y: x + y, my_list) / len(my_list) print(average)

**Output:**

`3`

**Explanation:**

In the above code, the reduce function takes two arguments: the first argument is a lambda function that adds the elements of the list together, and the second argument is the list itself. The lambda function in this program takes two arguments x and y and returns their sum. reduce applies this lambda function to the list in a cumulative manner, meaning it reduces the list to a single value by adding up all the elements. We then divide the sum by the length of the list to obtain the average.

**Summary**

In summary, an average function in Python is used to calculate the average value of a given set of numbers. There are several ways to implement an average function in Python, including using the built-in sum() and len() functions, using a for loop to iterate through the list of numbers, using built-in functions from the statistics module, or using the reduce() and lambda Functions. The choice of implementation depends on the specific requirements of the problem being solved.

## Frequently Asked Questions(FAQs)

**Q1: What is the average function in Python?**

**A:** The average function is a built-in function in Python’s statistics module that calculates the arithmetic mean of a list of numbers.

**Q2: What happens if I pass an empty list to the average function?**

**A:** If you pass an empty list to the average function, it will raise a StatisticsError with the message "mean requires at least one data point".

**Q3: Can the average function handle non-numeric data?**

**A:** No, the average function can only handle numeric data. If you pass a list of non-numeric data, such as strings or booleans, it will raise a TypeError with the message "unsupported operand type(s) for +: ‘int’ and ‘str’".

**Q4: Does the average function round the result?**

**A:** No, the average function does not round the result. It returns the exact arithmetic mean of the input list.

**Q5: What happens if I pass a single number to the average function?**

**A:** If you pass a single number to the average function, it will return that number. This is because the arithmetic mean of a single number is equal to that number itself.

**Q6: Can the average function handle NaN values?**

**A:** Yes, the average function can handle NaN (Not a Number) values in the input list. If the input list contains any NaN values, the function will return NaN. To handle NaN values, you can use the mean function from the NumPy module instead.