def smoke_python_name():
    # if this script is being run by py2.5 or greater,
    # then we assume that "python" points to a 2.5 or
    # greater python VM. otherwise, explicitly use 2.5
    # which we assume to be installed.
    import subprocess
    version = re.compile(r'[Pp]ython ([\d\.]+)', re.MULTILINE)
    binaries = ['python2.5', 'python2.6', 'python2.7', 'python25', 'python26', 'python27', 'python']
    for binary in binaries:
        try:
            # py-2.4 compatible replacement for shell backticks
            print 'about to try %s' % binary
            out, err = subprocess.Popen([binary, '-V'], stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()
            print 'subprocess executed for %s' % binary
            for stream in (out, err):
                match = version.search(stream)
                if match:
                    print '%s matched' % binary
                    versiontuple = tuple(map(int, match.group(1).split('.')))
                    if versiontuple >= (2, 5):
                        return binary
            print '%s did not match' % binary

        except Exception, e:
            print 'got exception %s when trying %s' % (e, binary)
            pass
    # if that all fails, fall back to "python"
    return "python"

========================================================================
OUTPUT :
========================================================================

scons: Reading SConscript files ...
scons version: 2.1.0
python version: 2 7 2 'final' 0
using system version of: snappy
using system version of: sm
using system version of: pcre
Checking whether the C++ compiler worksyes
Checking for C library stdc++... yes
Checking for C++ header file boost/filesystem/operations.hpp... yes
Checking for C library boost_system-mt... yes
Checking for C library boost_thread-mt... yes
Checking for C library boost_filesystem-mt... yes
Checking for C library boost_program_options-mt... yes
Checking for C++ header file execinfo.h... yes
Checking for C library pcap... yes
Checking whether the C++ compiler worksyes
Checking for C++ header file boost/filesystem/operations.hpp... yes
Checking for C library boost_system-mt... yes
Checking for C library boost_thread-mt... yes
Checking for C library boost_filesystem-mt... yes
Checking for C library boost_program_options-mt... yes
Checking for C++ header file execinfo.h... yes
Checking for C library pcap... yes
about to try python2.5
got exception [Errno 2] No such file or directory when trying python2.5
about to try python2.6