Build Dependencies
Build dependencies for Python-dependent packages must be declared for every Python version that the package is built for.
The python3-all-dev should be used when building extensions for any or all Python 3 versions. The python-all-dev should be used when building extensions for any or all Python 2 versions. To build for a specific version or versions, declare Build-Depends on pythonX.Y-dev.
Some applications and pure Python modules may be able to avoid dependency on the -dev packages, and declare Build-Depends on the runtime environment only (python3, python3-all, python, python-all). A package that does not require the -dev packages must not declare Build-Depends on them.
Declare Build-Depends on at least:

Build-Depends: python2.7
Build-Depends: python2.6 (>= 2.6-1)
Build-Depends: python (>= 2.6.6-9)
Build-Depends: python-all

Build-Depends: python2.7-dev
Build-Depends: python3.5-dev (>= 3.5.1-1)
Build-Depends: python-dev (>= 2.6.6-9)
Build-Depends: python-all-dev
Build-Depends: python3-all-dev (>= 3.2)