I need to setup environment with the path to a binary. In the shell, I can use which to find the path. Is there an equivalent in python?
This is my code.
cmd = ["which","abc"]
p = subprocess.Popen(cmd, stdout=subprocess.PIPE)
res = p.stdout.readlines()
if len(res) == 0: return False
return True
I know this is an older question, but if you happen to be using Python 3.3+ you can use shutil.which(cmd). You can find the documentation here. It has the advantage of being in the standard library.
An example would be like so:
>>> import shutil
>>> shutil.which("bash")
'/usr/bin/bash'
There is distutils.spawn.find_executable().
PATH via where.exe) for me on Windows.
$ touch bash; python3 -c "from distutils.spawn import find_executable; print(find_executable('bash'))" it prints out bash. Use shutil.which instead.There's not a command to do that, but you can iterate over environ["PATH"] and look if the file exists, which is actually what which does.
import os
def which(file):
for path in os.environ["PATH"].split(os.pathsep):
if os.path.exists(os.path.join(path, file)):
return os.path.join(path, file)
return None
Good luck!
os.path.sep instead of / and os.pathsep instead of :
You could try something like the following:
import os
import os.path
def which(filename):
"""docstring for which"""
locations = os.environ.get("PATH").split(os.pathsep)
candidates = []
for location in locations:
candidate = os.path.join(location, filename)
if os.path.isfile(candidate):
candidates.append(candidate)
return candidates
PATHEXT into account as wellIf you use shell=True, then your command will be run through the system shell, which will automatically find the binary on the path:
p = subprocess.Popen("abc", stdout=subprocess.PIPE, shell=True)
shell=True it is looked up in path, but it does not help if you want to find which of the possible commands exists.This is the equivalent of the which command, which not only checks if the file exists, but also whether it is executable:
import os
def which(file_name):
for path in os.environ["PATH"].split(os.pathsep):
full_path = os.path.join(path, file_name)
if os.path.exists(full_path) and os.access(full_path, os.X_OK):
return full_path
return None
Here's a one-line version of earlier answers:
import os
which = lambda y: next(filter(lambda x: os.path.isfile(x) and os.access(x,os.X_OK),[x+os.path.sep+y for x in os.getenv("PATH").split(os.pathsep)]),None)
used like so:
>>> which("ls")
'/bin/ls'
TypeError: list object is not an iterator.
whichitself is not a good choice for detecting if a command is installed. Referenceimport sys; sys.executable.