Source Code Question

[icbd]

When I initialized the Pipefile, pipenv helped me create the directory of virtualenv, e.g. creator CPython3Posix(dest=/Users/icbd/.local/share/virtualenvs/未命名文件夹-AsmMYtXt

I was curious about how the name of this directory was generated, so I found the source code implementation.

pipenv/pipenv/project.py

Lines 539 to 546 in 32e18cd

	def get_name(name, location):
	name = self._sanitize(name)
	hash = hashlib.sha256(location.encode()).digest()[:6]
	encoded_hash = base64.urlsafe_b64encode(hash).decode()
	return name, encoded_hash[:8]
	clean_name, encoded_hash = get_name(name, self.pipfile_location)
	venv_name = f"{clean_name}-{encoded_hash}"

Does the processing of base64.urlsafe_b64encode have any special considerations? It seems that using hex() would be enough.

Thanks

[oz123]

What would be the advantage of hex over base64.urlsafe_b64encode?

[matteius]

@icbd did you know you can specify the name of your virtualenv with an environment variable override as well?

[matteius]

1. Problem Summary:

The issue questions the use of base64.urlsafe_b64encode in generating a unique hash for the virtual environment directory name. The user believes using hex() might be sufficient and seeks clarification on the rationale behind the chosen method.

2. Comment Analysis:

• Another user inquires about the advantages of using hex() over base64.urlsafe_b64encode, highlighting the need to consider the benefits of the existing approach.
• The maintainer points out the possibility of specifying a custom virtual environment name via an environment variable, suggesting an alternative solution for the user's potential concern.

3. Proposed Resolution:

While the user's suggestion of using hex() to generate the hash is valid, base64.urlsafe_b64encode offers specific advantages in this context:

• Conciseness: Base64 encoding produces a shorter hash string compared to a hexadecimal representation for the same data. This results in shorter virtual environment directory names, improving readability and usability.
• URL Safety: The "urlsafe" variant of Base64 ensures that the generated hash is safe to use in file paths, avoiding characters that might be problematic for file systems.
• Collision Resistance: The hash is derived from the Pipfile location, providing reasonable collision resistance. Changing the hash generation algorithm should not increase the risk of collisions.

Therefore, continuing to use base64.urlsafe_b64encode remains a suitable approach for generating the virtual environment hash.

4. Code Snippet:

No code changes are necessary based on the current analysis.

5. Additional Steps:

• Documentation: Add a comment in the pipenv/project.py file explaining the rationale for using base64.urlsafe_b64encode for generating the virtual environment hash.
• Future Considerations: If the need arises for significantly shorter directory names, explore using a stronger hashing algorithm (e.g., SHA256) with a shorter output truncation.
• Address User Concern: While the maintainer has highlighted the option of using a custom virtual environment name, it would be beneficial to directly address the user's question about the choice of base64.urlsafe_b64encode in the issue thread, pointing to the documentation for further details.

By addressing the user's concerns and providing clear documentation, we can enhance understanding and maintain the benefits of the existing approach.