check dependencies example

checkdependencies.py

import subprocess



def check_dependencies():
    """Ensure required tools for installation are present.
    """
    print("Checking required dependencies")
    for cmd, param, url in [("git", '--version', "http://git-scm.com/"),
                     ("wget", '--version', "http://www.gnu.org/software/wget/"),
                     ("curl", '--version', "http://curl.haxx.se/"),
                     ('bzip2', '-h', 'www.bzip.org/')]:
        try:
            retcode = subprocess.call([cmd, param], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
        except OSError:
            retcode = 127
        if retcode == 127:
            raise OSError("Vallys requires %s (%s)" % (cmd, url))
        else:
            print " %s found" % cmd


check_dependencies()