#       
#  Overview 
The **`os.getenv()` method** is used to extract the value of the environment variable key if it exists. Otherwise, the default value will be returned.

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> Note: The **`os` module** in Python provides an interface to interact with the operating system.

# 
#  Syntax

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```python
os.getenv(key, default=None)
```
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# 
#  Parameters

This method takes the following values as an argument:

* **`key`**: This is the name of an environment variable.

* **`default=None`**: If a key does not exist, `default` will be set to `None`. `default` is an optional value.

##
## Return value

This method returns a string denoting the value of the environment variable. If it does not exist, it returns the value of the `default` parameter.

##
## Code

Let's see how to use the `getenv()` method in the code examples below:

##
## Example 1
Let's look at the code below:

import os  # importing os module

# defining Env variable with 'HOME' as value
key = "HOME"

# invoking getenv() method
value = os.getenv(key, default=None)
print(f"Value of env variable key='HOME': {value}")

# 
## Explanation 

* **Line 4**: We use the `'HOME'` as key.

* **Line 7**: We invoke the `os.getenv()` method to extract `key` parallel to this value.

## Output

The output is a value parallel to the specified key in an environment variable.

# 
## Example 2
Let's look at the code below:


import os  # importing os module

# value for env variable
key = 'PYTHON_USR'

# invokinig os.getenv() with default= 'python/edpresso'
value = os.getenv(key,default='python/edpresso')
print(f"Value of 'PYTHON_USR' env variable: {value}")

# 
## Explanation 

* **Line 4**: We use `key='PYTHON_USR'` for the environment variable to extract its value as a string. 

* **Line 7**: 
We invoke the `getenv()` method with `'PYTHON_USR'` as key and `'python/edpresso'` as the default value.

## Output

In the code snippet, the key-value `'PYTHON_USR'` does not exist in the environment variable. Therefore, the default value `'python/edpresso'` is returned.

What is os.getenv() method in Python?

Retrieves environment variable value using key; returns default if key is absent. Syntax: os.getenv(key, default=None).