Environment variables usage in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the module needed to access environment variables.

Python

import [1]

Drag options to blanks, or click blank then click option'

Asys

Bconfig

Cenv

Dos

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'sys' instead of 'os' because it also deals with system info.

Trying to import a non-existent module like 'env' or 'config'.

The os module is used in Python to access environment variables.

2fill in blank

medium

Complete the code to get the value of the environment variable named 'HOME'.

Python

home_dir = os.[1]('HOME')

Drag options to blanks, or click blank then click option'

Agetenvvalue

Bgetenvs

Cgetenv

Dgetenv_var

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect function names like 'getenvs' or 'getenv_var'.

Trying to access environment variables as dictionary keys without importing os.

The os.getenv() function returns the value of an environment variable.

3fill in blank

hard

Fix the error in the code to set an environment variable 'API_KEY' to '12345'.

Python

os.[1]['API_KEY'] = '12345'

Drag options to blanks, or click blank then click option'

Aenviron

Bsetenv

Cputenv

Dset

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'setenv' which is a function but not used like this in Python.

Trying to call 'putenv' as a dictionary.

Using 'set' which is not a valid method here.

To set an environment variable, assign it in os.environ like a dictionary.

4fill in blank

hard

Fill both blanks to create a dictionary of environment variables whose names start with 'APP_'.

Python

app_vars = {key: os.environ[key] for key in os.environ if key [1] 'APP_'}

Drag options to blanks, or click blank then click option'

Astartswith

Bendswith

Ccontains

Dequals

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'endswith' which checks the end of the string.

Using 'contains' which is not a string method.

Using 'equals' which checks full equality.

The startswith method checks if a string begins with a given substring.

5fill in blank

hard

Fill all three blanks to safely get an environment variable 'PORT' as an integer with default 8080.

Python

port = int(os.getenv('[1]', [2])) if os.getenv('[3]') else 8080

Drag options to blanks, or click blank then click option'

APORT

B'8080'

D'80'

Attempts:

3 left

💡 Hint

Common Mistakes

Using integer 8080 directly as default in getenv, which expects a string.

Using different variable names inconsistently.

Not checking if the environment variable exists before converting.

This code tries to get 'PORT' from environment variables. If it exists, it converts it to an integer. If not, it uses 8080 as default.

Practice

1. What is the main purpose of using environment variables in a Python program?

easy

A. To print output on the screen

B. To write data to files

C. To create new Python functions

D. To store configuration settings outside the code

Solution

1. Step 1: Understand environment variables role

   Environment variables hold settings or secrets outside the program code.

2. Step 2: Identify correct purpose

   Using environment variables helps keep code flexible and secure by not hardcoding values.

3. Final Answer:

   To store configuration settings outside the code -> Option D

4. Quick Check:

   Environment variables = external settings [OK]

Hint: Environment variables hold settings outside code [OK]

Common Mistakes:

• Thinking environment variables store data inside the program
• Confusing environment variables with file operations
• Assuming environment variables create functions

2. Which of the following is the correct way to import the module needed to access environment variables in Python?

easy

A. import environment

B. import os

C. import sys

D. import env

Solution

1. Step 1: Recall Python module for environment variables

   The standard module to access environment variables is os.

2. Step 2: Check options for correct import

   Only import os is correct; others are invalid or unrelated.

3. Final Answer:

   import os -> Option B

4. Quick Check:

   Module for env vars = os [OK]

Hint: Use 'import os' to access environment variables [OK]

Common Mistakes:

• Using 'import environment' which does not exist
• Confusing 'sys' module with environment variables
• Trying to import 'env' which is not a standard module

3. What will be the output of this code if the environment variable USER is set to alice?

import os
name = os.getenv('USER', 'guest')
print(name)

medium

A. alice

B. USER

C. null

D. guest

Solution

1. Step 1: Understand os.getenv behavior

   os.getenv('USER', 'guest') returns the value of USER if set, else 'guest'.

2. Step 2: Apply given environment variable value

   Since USER is set to 'alice', the function returns 'alice'.

3. Final Answer:

   alice -> Option A

4. Quick Check:

   os.getenv returns env var value if set [OK]

Hint: os.getenv returns env var value or default [OK]

Common Mistakes:

• Assuming default is always returned
• Printing the variable name instead of its value
• Confusing null with default value

4. Identify the error in this code snippet that tries to read an environment variable:

import os
api_key = os.getenv('API_KEY')
print(api_key.upper())

Assume API_KEY is not set in the environment.

medium

A. AttributeError because api_key is null

B. SyntaxError due to missing parentheses

C. No error, code runs fine

D. NameError because os is not imported

Solution

1. Step 1: Check os.getenv return when variable missing

   When API_KEY is not set, os.getenv returns null.

2. Step 2: Understand method call on null

   Calling upper() on null causes an AttributeError because null has no such method.

3. Final Answer:

   AttributeError because api_key is null -> Option A

4. Quick Check:

   null.upper() causes AttributeError [OK]

Hint: Check for null before calling string methods [OK]

Common Mistakes:

• Assuming os.getenv returns empty string if missing
• Ignoring that null has no string methods
• Thinking code runs without error

5. You want to safely read an environment variable PORT as an integer with a default of 8080 if not set or invalid. Which code snippet correctly does this?

hard

A. port = int(os.getenv('PORT') or 8080)

B. port = os.getenv('PORT', 8080)

C. try:\n port = int(os.getenv('PORT'))\nexcept (TypeError, ValueError):\n port = 8080

D. port = int(os.getenv('PORT', 8080))

Solution

1. Step 1: Understand the problem requirements

   We must convert PORT to int, use 8080 if missing or invalid (non-integer).

2. Step 2: Analyze each option

   port = int(os.getenv('PORT', 8080)) fails if PORT is set but not an integer string (raises ValueError). port = os.getenv('PORT', 8080) does not convert to int. port = int(os.getenv('PORT') or 8080) uses or but fails if PORT is set to invalid string (ValueError). try:\n port = int(os.getenv('PORT'))\nexcept (TypeError, ValueError):\n port = 8080 uses try-except to handle missing or invalid values safely.

3. Final Answer:

   try:\n port = int(os.getenv('PORT'))\nexcept (TypeError, ValueError):\n port = 8080 -> Option C

4. Quick Check:

   Use try-except to safely convert env var [OK]

Hint: Use try-except to handle invalid env var conversions [OK]

Common Mistakes:

• Not handling invalid integer strings
• Assuming default works if env var is invalid
• Not converting string to int