def find_graphviz():
    """Locate Graphviz's executables in the system.

    Tries three methods:

    First: Windows Registry (Windows only)
    This requires Mark Hammond's pywin32 is installed.

    Secondly: Search the path
    It will look for 'dot', 'twopi' and 'neato' in all the directories
    specified in the PATH environment variable.

    Thirdly: Default install location (Windows only)
    It will look for 'dot', 'twopi' and 'neato' in the default install
    location under the "Program Files" directory.

    It will return a dictionary containing the program names as keys
    and their paths as values.

    If this fails, it returns None.
    """

    # Method 1 (Windows only)
    if os.sys.platform == 'win32':

        HKEY_LOCAL_MACHINE = 0x80000002
        KEY_QUERY_VALUE = 0x0001

        RegOpenKeyEx = None
        RegQueryValueEx = None
        RegCloseKey = None

        try:
            import win32api
            RegOpenKeyEx = win32api.RegOpenKeyEx
            RegQueryValueEx = win32api.RegQueryValueEx
            RegCloseKey = win32api.RegCloseKey

        except ImportError:
            # Print a messaged suggesting they install these?
            pass

        try:
            import ctypes

            def RegOpenKeyEx(key, subkey, opt, sam):
                result = ctypes.c_uint(0)
                ctypes.windll.advapi32.RegOpenKeyExA(key, subkey, opt, sam,
                                                     ctypes.byref(result))
                return result.value

            def RegQueryValueEx(hkey, valuename):
                data_type = ctypes.c_uint(0)
                data_len = ctypes.c_uint(1024)
                data = ctypes.create_string_buffer(1024)

                # this has a return value, which we should probably check
                ctypes.windll.advapi32.RegQueryValueExA(
                    hkey, valuename, 0, ctypes.byref(data_type),
                    data, ctypes.byref(data_len))

                return data.value

            RegCloseKey = ctypes.windll.advapi32.RegCloseKey

        except ImportError:
            # Print a messaged suggesting they install these?
            pass

        if RegOpenKeyEx is not None:
            # Get the GraphViz install path from the registry
            hkey = None
            potentialKeys = [
                "SOFTWARE\\ATT\\Graphviz",
                "SOFTWARE\\AT&T Research Labs\\Graphviz"]
            for potentialKey in potentialKeys:

                try:
                    hkey = RegOpenKeyEx(
                        HKEY_LOCAL_MACHINE,
                        potentialKey, 0, KEY_QUERY_VALUE)

                    if hkey is not None:
                        path = RegQueryValueEx(hkey, "InstallPath")
                        RegCloseKey(hkey)

                        # The regitry variable might exist, left by
                        # old installations but with no value, in those cases
                        # we keep searching...
                        if not path:
                            continue

                        # Now append the "bin" subdirectory:
                        path = os.path.join(path, "bin")
                        progs = __find_executables(path)
                        if progs is not None:
                            return progs

                except Exception:
                    pass
                else:
                    break

    # Method 2 (Linux, Windows etc)
    if 'PATH' in os.environ:
        for path in os.environ['PATH'].split(os.pathsep):
            progs = __find_executables(path)
            if progs is not None:
                return progs

    # Method 3 (Windows only)
    if os.sys.platform == 'win32':

        # Try and work out the equivalent of "C:\Program Files" on this
        # machine (might be on drive D:, or in a different language)
        if 'PROGRAMFILES' in os.environ:
            # Note, we could also use the win32api to get this
            # information, but win32api may not be installed.
            path = os.path.join(os.environ['PROGRAMFILES'], 'ATT',
                                'GraphViz', 'bin')
        else:
            # Just in case, try the default...
            path = r"C:\Program Files\att\Graphviz\bin"

        progs = __find_executables(path)

        if progs is not None:
            return progs

    for path in (
            '/usr/bin', '/usr/local/bin',
            '/opt/local/bin',
            '/opt/bin', '/sw/bin', '/usr/share',
            '/Applications/Graphviz.app/Contents/MacOS/'):

        progs = __find_executables(path)
        if progs is not None:
            return progs

    # Failed to find GraphViz
    return None
def find_graphviz ( ) : if os . sys . platform == 'win32' : HKEY_LOCAL_MACHINE = 0x80000002 KEY_QUERY_VALUE = 0x0001 RegOpenKeyEx = None RegQueryValueEx = None RegCloseKey = None try : import win32api RegOpenKeyEx = win32api . RegOpenKeyEx RegQueryValueEx = win32api . RegQueryValueEx RegCloseKey = win32api . RegCloseKey except ImportError : pass try : import ctypes def RegOpenKeyEx ( key , subkey , opt , sam ) : result = ctypes . c_uint ( 0 ) ctypes . windll . advapi32 . RegOpenKeyExA ( key , subkey , opt , sam , ctypes . byref ( result ) ) return result . value def RegQueryValueEx ( hkey , valuename ) : data_type = ctypes . c_uint ( 0 ) data_len = ctypes . c_uint ( 1024 ) data = ctypes . create_string_buffer ( 1024 ) ctypes . windll . advapi32 . RegQueryValueExA ( hkey , valuename , 0 , ctypes . byref ( data_type ) , data , ctypes . byref ( data_len ) ) return data . value RegCloseKey = ctypes . windll . advapi32 . RegCloseKey except ImportError : pass if RegOpenKeyEx is not None : hkey = None potentialKeys = [ "SOFTWARE\\ATT\\Graphviz" , "SOFTWARE\\AT&T Research Labs\\Graphviz" ] for potentialKey in potentialKeys : try : hkey = RegOpenKeyEx ( HKEY_LOCAL_MACHINE , potentialKey , 0 , KEY_QUERY_VALUE ) if hkey is not None : path = RegQueryValueEx ( hkey , "InstallPath" ) RegCloseKey ( hkey ) if not path : continue path = os . path . join ( path , "bin" ) progs = __find_executables ( path ) if progs is not None : return progs except Exception : pass else : break if 'PATH' in os . environ : for path in os . environ [ 'PATH' ] . split ( os . pathsep ) : progs = __find_executables ( path ) if progs is not None : return progs if os . sys . platform == 'win32' : if 'PROGRAMFILES' in os . environ : path = os . path . join ( os . environ [ 'PROGRAMFILES' ] , 'ATT' , 'GraphViz' , 'bin' ) else : path = r"C:\Program Files\att\Graphviz\bin" progs = __find_executables ( path ) if progs is not None : return progs for path in ( '/usr/bin' , '/usr/local/bin' , '/opt/local/bin' , '/opt/bin' , '/sw/bin' , '/usr/share' , '/Applications/Graphviz.app/Contents/MacOS/' ) : progs = __find_executables ( path ) if progs is not None : return progs return None
Locate Graphviz's executables in the system.

    Tries three methods:

    First: Windows Registry (Windows only)
    This requires Mark Hammond's pywin32 is installed.

    Secondly: Search the path
    It will look for 'dot', 'twopi' and 'neato' in all the directories
    specified in the PATH environment variable.

    Thirdly: Default install location (Windows only)
    It will look for 'dot', 'twopi' and 'neato' in the default install
    location under the "Program Files" directory.

    It will return a dictionary containing the program names as keys
    and their paths as values.

    If this fails, it returns None.