| try: |
| from shutil import which # Python >= 3.3 |
| except ImportError: |
| import os, sys |
| |
| # This is copied from Python 3.4.1 |
| def which(cmd, mode=os.F_OK | os.X_OK, path=None): |
| """Given a command, mode, and a PATH string, return the path which |
| conforms to the given mode on the PATH, or None if there is no such |
| file. |
| |
| `mode` defaults to os.F_OK | os.X_OK. `path` defaults to the result |
| of os.environ.get("PATH"), or can be overridden with a custom search |
| path. |
| |
| """ |
| # Check that a given file can be accessed with the correct mode. |
| # Additionally check that `file` is not a directory, as on Windows |
| # directories pass the os.access check. |
| def _access_check(fn, mode): |
| return (os.path.exists(fn) and os.access(fn, mode) |
| and not os.path.isdir(fn)) |
| |
| # If we're given a path with a directory part, look it up directly rather |
| # than referring to PATH directories. This includes checking relative to the |
| # current directory, e.g. ./script |
| if os.path.dirname(cmd): |
| if _access_check(cmd, mode): |
| return cmd |
| return None |
| |
| if path is None: |
| path = os.environ.get("PATH", os.defpath) |
| if not path: |
| return None |
| path = path.split(os.pathsep) |
| |
| if sys.platform == "win32": |
| # The current directory takes precedence on Windows. |
| if not os.curdir in path: |
| path.insert(0, os.curdir) |
| |
| # PATHEXT is necessary to check on Windows. |
| pathext = os.environ.get("PATHEXT", "").split(os.pathsep) |
| # See if the given file matches any of the expected path extensions. |
| # This will allow us to short circuit when given "python.exe". |
| # If it does match, only test that one, otherwise we have to try |
| # others. |
| if any(cmd.lower().endswith(ext.lower()) for ext in pathext): |
| files = [cmd] |
| else: |
| files = [cmd + ext for ext in pathext] |
| else: |
| # On other platforms you don't have things like PATHEXT to tell you |
| # what file suffixes are executable, so just pass on cmd as-is. |
| files = [cmd] |
| |
| seen = set() |
| for dir in path: |
| normdir = os.path.normcase(dir) |
| if not normdir in seen: |
| seen.add(normdir) |
| for thefile in files: |
| name = os.path.join(dir, thefile) |
| if _access_check(name, mode): |
| return name |
| return None |
| |
| |
| class PtyProcessError(Exception): |
| """Generic error class for this package.""" |