I would like to include the current git hash in the output of a Python script (as a the version number of the code that generated that output).

How can I access the current git hash in my Python script?

The git describe command is a good way of creating a human-presentable “version number” of the code. From the examples in the documentation:

With something like git.git current tree, I get:

[torvalds@g5 git]$ git describe parent
v1.0.4-14-g2414721

i.e. the current head of my “parent” branch is based on v1.0.4, but since it has a few commits on top of that, describe has added the number of additional commits (“14”) and an abbreviated object name for the commit itself (“2414721”) at the end.

From within Python, you can do something like the following:

import subprocess
label = subprocess.check_output(["git", "describe"]).strip()

No need to hack around getting data from the git command yourself. GitPython is a very nice way to do this and a lot of other git stuff. It even has “best effort” support for Windows.

After pip install gitpython you can do

import git
repo = git.Repo(search_parent_directories=True)
sha = repo.head.object.hexsha

Something to consider when using this library. The following is taken from gitpython.readthedocs.io

Leakage of System Resources

GitPython is not suited for long-running processes (like daemons) as it tends to leak system resources. It was written in a time where destructors (as implemented in the __del__ method) still ran deterministically.

In case you still want to use it in such a context, you will want to search the codebase for __del__ implementations and call these yourself when you see fit.

Another way assure proper cleanup of resources is to factor out GitPython into a separate process which can be dropped periodically

This post contains the command, Greg’s answer contains the subprocess command.

import subprocess

def get_git_revision_hash():
    return subprocess.check_output(['git', 'rev-parse', 'HEAD'])

def get_git_revision_short_hash():
    return subprocess.check_output(['git', 'rev-parse', '--short', 'HEAD'])

numpy has a nice looking multi-platform routine in its setup.py:

import os
import subprocess

# Return the git revision as a string
def git_version():
    def _minimal_ext_cmd(cmd):
        # construct minimal environment
        env = {}
        for k in ['SYSTEMROOT', 'PATH']:
            v = os.environ.get(k)
            if v is not None:
                env[k] = v
        # LANGUAGE is used on win32
        env['LANGUAGE'] = 'C'
        env['LANG'] = 'C'
        env['LC_ALL'] = 'C'
        out = subprocess.Popen(cmd, stdout = subprocess.PIPE, env=env).communicate()[0]
        return out

    try:
        out = _minimal_ext_cmd(['git', 'rev-parse', 'HEAD'])
        GIT_REVISION = out.strip().decode('ascii')
    except OSError:
        GIT_REVISION = "Unknown"

    return GIT_REVISION

If subprocess isn’t portable and you don’t want to install a package to do something this simple you can also do this.

import pathlib

def get_git_revision(base_path):
    git_dir = pathlib.Path(base_path) / '.git'
    with (git_dir / 'HEAD').open('r') as head:
        ref = head.readline().split(' ')[-1].strip()

    with (git_dir / ref).open('r') as git_hash:
        return git_hash.readline().strip()

I’ve only tested this on my repos but it seems to work pretty consistantly.

Here’s a more complete version of Greg’s answer:

import subprocess
print(subprocess.check_output(["git", "describe", "--always"]).strip().decode())

Or, if the script is being called from outside the repo:

import subprocess, os
os.chdir(os.path.dirname(__file__))
print(subprocess.check_output(["git", "describe", "--always"]).strip().decode())

If you don’t have git available for some reason, but you have the git repo (.git folder is found), you can fetch the commit hash from .git/fetch/heads/[branch]

For example, I’ve used a following quick-and-dirty Python snippet run at the repository root to get the commit id:

git_head = '.git\\HEAD'

# Open .git\HEAD file:
with open(git_head, 'r') as git_head_file:
    # Contains e.g. ref: ref/heads/master if on "master"
    git_head_data = str(git_head_file.read())

# Open the correct file in .git\ref\heads\[branch]
git_head_ref = '.git\\%s' % git_head_data.split(' ')[1].replace('/', '\\').strip()

# Get the commit hash ([:7] used to get "--short")
with open(git_head_ref, 'r') as git_head_ref_file:
    commit_id = git_head_ref_file.read().strip()[:7]