Isolating Dependencies With Virtual Environments

Hi Dan, do you have any other courses where i can learn about pylint and pytest (writing and executing unit tests) and integrating these in a CI pipeline?

Hi aravind, check out these three courses:

• Test-Driven Development With PyTest
• Writing Cleaner Python Code With PyLint
• Continuous Integration With Python

I also recommend that you take a look at this learning path:

realpython.com/learning-paths/test-your-python-apps

Hi Dan, thanks. I will go through the links.

Meanwhile, do you have a video or upcoming course on “TOX”? I think its tox.readthedocs.io/en/latest/. * Tox vs. PyTest * When to use which * Pros/Cons of each * Sample test cases using Tox

Yep, we do have a Python testing tutorial on tox. pytest and tox do two completely different things, so it’s not really a “pytest vs tox” question IMO. But you’ll hear all about it in the tutorial I linked above :)

Fantastic, Dan - really loving the courses on this website and also the support in the comments/forums - keep up the great work & looking forward to purchasing further courses!

Why can’t we just always make sure we are keeping our software versions up to date instead of using virtual environments?

The only reason I can think of, is that, we can’t be sure that the latest version of a package won’t break our software.

I would really appreciate input into this because I have very little confidence in the efficiency of virtual environments.

@Bobby Tagget When you work on a single hobby project where you’re the only developer, then using virtual environments can indeed seem redundant because you generally want to use the latest versions of your dependencies. However, virtual environments help solve problems that may arise when you work on multiple projects simultaneously or if you’re a member of a larger team.

More specifically, different projects often depend on different versions of the same library. Without isolated virtual environments per project, this could lead to version conflicts, informally known as dependency hell. The larger your project, the bigger of a problem this becomes because it’s more likely to have a conflict.

Other than that, virtual environments ensure reproducibility, which helps other team members work on exactly the same library versions as yours. When deploying your project to a remote environment, you also want it to use the expected library versions as opposed to whatever comes installed on that machine.

Hello, I am using Visual Source code (VSC) for my Pythond development project. Is that comes with virtual environment or do we need to install specific applications to create and use virtual environment for python projects?

Thanks, Venkat

@Dan, @Bartosz, While working in corporate environments, we are mostly under proxy network and while in proxy, it becomes hard to install new packages using pip. Do we have any good course or tutorial on how to install packages under proxy network? This would be of great help.

Thanks,

Venkat

@dakshnavenki The proxy server is likely there for a reason, in order to prevent employees from installing software from unauthorized sources. To bypass this restriction, some development teams set up a local PyPI server that proxies requests to the official one. Additionally, it can host proprietary modules that should never be published to the official PyPI, e.g., to avoid accidental leaks.

However, to route traffic through your company’s proxy server, you can use the --proxy option of the pip command, as shown below:

$ python -m pip install requests --proxy http://proxy.server:1234

If the proxy requires authentication, then you can optionally include your credentials:

$ python -m pip install requests --proxy http://user:password@proxy.server:1234

Let us know if that helps!

Thanks for the answer Bartosz, but I’m not able to get it worked. I’ve given the response on pip install command below, both with and without --proxy option. Please correct me where I am going wrong and what’s the exact issue.

Without proxy option:

C:\Users\vdhatchanamoorthy>pip install requests

*Defaulting to user installation because normal site-packages is not writeable
Looking in indexes: https://repos.proxy.l-5com.com/artifactory/api/pypi/pypi/simple
WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by *'ConnectTimeoutError(<pip._vendor.urllib3.connection.HTTPSConnection object at 0x00000239A35F9FC0>, 'Connection to repos.proxy.l-3com.com timed out. (connect timeout=15)')': /artifactory/api/pypi/pypi/simple/requests/
WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ConnectTimeoutError(<pip._vendor.urllib3.connection.HTTPSConnection object at 0x00000239A35FA2C0>, 'Connection to repos.proxy.l-3com.com timed out. (connect timeout=15)')': /artifactory/api/pypi/pypi/simple/requests/
WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ConnectTimeoutError(<pip._vendor.urllib3.connection.HTTPSConnection object at 0x00000239A35FA500>, 'Connection to repos.proxy.l-3com.com timed out. (connect timeout=15)')': /artifactory/api/pypi/pypi/simple/requests/
WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ConnectTimeoutError(<pip._vendor.urllib3.connection.HTTPSConnection object at 0x00000239A35FA740>, 'Connection to repos.proxy.l-3com.com timed out. (connect timeout=15)')': /artifactory/api/pypi/pypi/simple/requests/
WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ConnectTimeoutError(<pip._vendor.urllib3.connection.HTTPSConnection object at 0x00000239A35FA980>, 'Connection to repos.proxy.l-3com.com timed out. (connect timeout=15)')': /artifactory/api/pypi/pypi/simple/requests/
ERROR: Could not find a version that satisfies the requirement requests (from versions: none)
ERROR: No matching distribution found for requests

With Proxy option:

C:\Users\vdhatchanamoorthy>pip install requests --proxy servername:XXXX
*Defaulting to user installation because normal site-packages is not writeable
Looking in indexes: https://repos.proxy.l-5com.com/artifactory/api/pypi/pypi/simple
WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', OSError('Tunnel connection failed: 400 '))': /artifactory/api/pypi/pypi/simple/requests/
WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', OSError('Tunnel connection failed: 400 '))': /artifactory/api/pypi/pypi/simple/requests/
WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', OSError('Tunnel connection failed: 400 '))': /artifactory/api/pypi/pypi/simple/requests/
WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', OSError('Tunnel connection failed: 400 '))': /artifactory/api/pypi/pypi/simple/requests/
WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', OSError('Tunnel connection failed: 400 '))': /artifactory/api/pypi/pypi/simple/requests/
ERROR: Could not find a version that satisfies the requirement requests (from versions: none)
ERROR: No matching distribution found for requests*

Thanks, Venkat

@dakshnavenki It seems that, regardless of whether the --proxy option is specified, pip is routing through your company’s local PyPI server, which appears to be hosted on top of Artifactory. The timeout and tunnel errors indicate that the issue might be due to one of the following:

• Incorrect proxy server or port configuration
• Invalid proxy credentials
• The proxy server blocking access to the repository URL
• A misconfigured or non-functional proxy server

It’s difficult for me to pinpoint the exact cause without further details, but these are some possible areas you might investigate.

Thank you for the response, Bartosz. I would try to get in touch with IT team to resolve this and get back to you if I need more help on this. Thank you so much.

Venkat