What is the meaning of conda's build string?

Question

If I run conda info sphinx from the command line, the last entry as of August 24, 2017, is

sphinx 1.6.3 py36_0
-------------------
file name   : sphinx-1.6.3-py36_0.tar.bz2
name        : sphinx
version     : 1.6.3
build string: py36_0
...

What is the meaning of the build string, which is mirrored above in the package version? Is this the minimum version of the python interpereter required by a package?

Answer 1

The first part of the build string (pyXX) of this package tells you the exact version of the Python interpreter that this package can be used for. Most likely, there are other packages for other versions of Python (py27, py35, etc.). The second part (after the underscore) tells you the build number of this package. The build number is typically incremented when there is a change in the build recipe, but no change in the version of the software being built. You can find more information in the description of the info/index.json fields.

Note, however, that the build string will be changing with conda build 3.0.

Package maintainers can customize their build strings using meta.yml (see Conda Build Documentation on Build section).