Tags Go , Python

Programmers that come to Go from Python often wonder "do I need something like virtualenv here?"

The short answer is NO; this post will provide some additional details.

While virtualenv in Python is useful in many situations, I think it'd be fair to divide them into two broad scenarios: for execution and for development. Let's see what Go offers for each of these scenarios.


There are multiple, mutually-incompatible versions of Python out in the wild. There are even multiple versions of the packaging tools (like pip). On top of this, different programs need different packages, often themselves with mutually-incompatible versions.

Python code typically expects to be installed, and expects to find packages it depends on installed in a central location. This can be an issue for systems where we don't have the permission to install packages/code to a central location.

All of this makes distributing Python applications quite tricky. It's common to use bundling tools like PyInstaller, but virtualenv is also a popular option [1].

Go is a statically compiled language, so this is a non-problem! Binaries are easy to build and distribute; the binary is a native executable for a given platform (just like a native executable built from C or C++ source), and has no dependencies on compiler or package versions. While you can install Go programs into a central location, you by no means have to do this. In fact, you typically don't have to install Go programs at all. Just invoke the binary.

It's also worth mentioning that Go has great cross-compilation support, making it easy to create binaries for multiple OSes from a single development machine.


Consider the following situation: you're developing a package, which depends on N other packages at specific versions; e.g. you need package foo at version 1.2 or above. Your system may have an older version of foo installed - 0.9; you try to upgrade it to 1.2 and some other program breaks. Now, this all sounds very manageable for package foo - how hard can it be to upgrade the uses of this simple package?

Reality is more difficult. foo could be Django; your code depends on a new version, while some other critical systems depend on an old version. Good luck fixing this conundrum. In Python, viruatenv is a critical tool to make such situations manageable; newer tools like pipenv wrap virtualenv with more usability patterns.

How about Go?

If you're using Go modules, this situation is very easy to handle. In a way, a Go module serves as its own virtualenv. Your go.mod file specifies the exact versions of dependency packages needed for your development, and these versions don't mix up with packages you need to develop some other project (which has its own go.mod).

Moreover, Go module directives like replace make it easy to short-circuit dependencies to try local patches. While debugging your project you find that package foo has a bug that may be affecting you? Want to try a quick fix and see if you're right? No problem, just clone foo locally, apply a fix, and use a replace to use this locally patched foo. Tools like gohack automate this process in a very convenient way.

What about different Go versions? Suppose you have to investigate a user report complaining that your code doesn't work with an older Go version. Or maybe you're curious to see how the upcoming beta release of a Go version will affect you. Go makes it easy to install different versions locally. These different versions have their own standard libraries that won't interfere with each other.

[1]Fun fact: this blog uses the Pelican static site generator. To regenerate the site I run Pelican in a virtualenv because I need a specific version of Pelican with some personal patches.