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|
- 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."""
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