# 
#  Problem statement

Given a list of numbers, find the average.

---
> The **average** is the sum of elements divided by the number of elements.
---

##  
## Example

* Input: `[1, 2, 3, 4, 5, 6, 7, 8,9]`

* Output: `5.0`

### Explanation

* Sum of elements = 1+2+3+4+5+6+7+8+9 = 45
* Number of elements = 9

* Average = $\frac{45}{9}$ = 5.0

#   
## Solution

We can solve this problem with the following methods:

* The `sum()` method
* The `reduce()` and `lambda` methods
* The `mean()` method

# 
## The `sum()` method

We will use the `sum()` and `len()` methods to find the average. 

* **`sum()`** is used to find the sum of elements in the list.

* **`len()`** is used to find the number of elements in the list.

In the code snippet below: 

* In line 1, we initialize the list `list_of_numbers` with `[1,2,3,4,5,6,7,8,9]`.

* In line 5, we divide the sum of the elements by the number of elements to find the average.

* In line 8, we print the average to the console.

#initializing the list with numbers
list_of_numbers = [1,2,3,4,5,6,7,8,9]

#find average
avg = sum(list_of_numbers) / len(list_of_numbers)

#print average
print(avg)


#  
## The `reduce()` and `lambda` methods

We use **`reduce()`** and **`lambda`** to calculate the sum of the elements in the list.

The following code snippet is the same as above, except for line 7, where we calculate the sum with `reduce()`  and `lambda`.

from functools import reduce

#initializing the list with numbers
list_of_numbers = [1,2,3,4,5,6,7,8,9]

#find average
avg = reduce(lambda a, b: a + b, list_of_numbers) / len(list_of_numbers)

#print average
print(avg)

#  
## The `mean()` method

We can use Python's built-in **`mean()`** function to calculate the average of a list.

The following code snippet is the same as above, except for line 7, where we can find the average directly with the `mean()` method.

from statistics import mean

#initializing the list with numbers
list_of_numbers = [1,2,3,4,5,6,7,8,9]

#find average
avg = mean(list_of_numbers)

#print average
print(avg)

How to find the average of a list in Python

Use sum() and len(), reduce() with lambda, or Python's mean() to find a list's average.

How to find the average of a list in Python

Problem statement

Example

Explanation

Solution

The sum() method

The reduce() and lambda methods

The mean() method

The `sum()` method

The `reduce()` and `lambda` methods

The `mean()` method