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Python Virtual Environments Lab

· 3 min read

1. Create the Environment​

# Linux/macOS
python3 -m venv my_devsecops_env

2. Activate it​

# Linux/macOS
source my_devsecops_env/bin/activate
# (You will see '(my_devsecops_env)' appear in your terminal prompt)

3. Install a library and verify​

pip install requests
pip list  # Only shows 'requests' and basic tools

4. Deactivate​

deactivate
pip list  # Shows your global system libraries (requests will be missing)

Lab 1: Troubleshooting Naming & Data Type "Crashes"​

Objective: Learn to identify and fix common syntax and logic errors in Python scripts.

Scenario: A junior developer has written a script to track security vulnerabilities, but it is failing. You need to fix it.

The Broken Code:

1st_tool = "Bandit"
scanner-status = "Active"
total vulnerabilities = 5
print("Scanning with " + 1st_tool)
print("Vulnerabilities found: " + total vulnerabilities)

Task:

  • Fix the variable naming violations (Starting with number, hyphen, and spaces).

  • Fix the TypeError when printing the vulnerabilities (Type Casting).

Solution (The Architect Way):

tool_01 = "Bandit"
scanner_status = "Active"
total_vulnerabilities = 5
# Using f-string for clean output
print(f"Scanning with {tool_01}")
print(f"Vulnerabilities found: {total_vulnerabilities}")

Lab 2: The "Dependency Conflict" Simulation​

Objective: Understand why venv is mandatory by intentionally breaking and then fixing a project environment.

Scenario: You have two DevSecOps scripts. Project A requires an old version of the requests library (2.10.0), but Project B requires the latest version.

Task:

  • Step 1: Create a directory named project_a and another named project_b.

  • Step 2: Inside project_a, create a venv, activate it, and run pip install requests==2.10.0.

  • Step 3: Inside project_b, create a separate venv, activate it, and run pip install requests==2.31.0.

  • Step 4: Run pip list in both to verify that Project A's version did not change when you installed Project B's version.

Verification:

  • Run python -c "import requests; print(requests.__version__)" in both environments. You should see different numbers!

Lab 3: Creating a Reproducible CI/CD Environment​

Objective: Learn to "Freeze" an environment so it can be recreated on any Linux server or GitHub Actions runner.

Scenario: You have finished developing a Python script for AWS IAM auditing. Now you need to give it to your DevOps team to run it in the pipeline.

Task:

  • Create a virtual environment and activate it.

  • Install the following DevSecOps libraries:

  • pip install boto3 (AWS SDK)

  • pip install bandit (Security Linter)

  • pip install safety (Dependency Checker)

  • The "Freeze" Step: Generate a requirements file:Bashpip freeze > requirements.txt

  • The "Recreation" Step: Deactivate the current venv, create a brand new one called prod_env, and install everything using only the file:Bashsource prod_env/bin/activate pip install -r requirements.txt

Architect Tip: Check the requirements.txt file. You will see not just the 3 libraries you installed, but also their "Sub-dependencies." This ensures 100% environment consistency.