How to check if a user exists in a GNU/Linux OS using Python?

Question

What is the easiest way to check the existence of a user on a GNU/Linux OS, using Python?

Anything better than issuing ls ~login-name and checking the exit code?

And if running under Windows?

score 42 · Accepted Answer · edited May 23 '17 at 12:16

42

This answer builds upon the answer by Brian. It adds the necessary try...except block.

Check if a user exists:

import pwd

try:
    pwd.getpwnam('someusr')
except KeyError:
    print('User someusr does not exist.')

Check if a group exists:

import grp

try:
    grp.getgrnam('somegrp')
except KeyError:
    print('Group somegrp does not exist.')

edited May 23 '17 at 12:16

Community

answered Mar 01 '13 at 23:23

Asclepius

score 10 · Answer 2 · answered Mar 29 '10 at 18:57

10

To look up my userid (bagnew) under Unix:

import pwd
pw = pwd.getpwnam("bagnew")
uid = pw.pw_uid

See the pwd module info for more.

answered Mar 29 '10 at 18:57

Brian Agnew

1

It will raise `KeyError` if the username is not found. – Joe Koberg Mar 29 '10 at 18:59
I have now added an answer with the necessary `try...except` block. – Asclepius Mar 01 '13 at 23:24

score 5 · Answer 3 · edited May 17 '18 at 20:01

5

Using pwd you can get a listing of all available user entries using pwd.getpwall(). This can work if you do not like try:/except: blocks.

import pwd

username = "zomobiba"
usernames = [x[0] for x in pwd.getpwall()]
if username in usernames:
    print("Yay")

edited May 17 '18 at 20:01

Asclepius

answered Mar 29 '10 at 21:25

Powertieke

4

Okay, but there is no reason not to like `try...except` blocks. It is also more efficient to query a single user with `getpwnam` than to query all users with `getpwall`. – Asclepius Mar 01 '13 at 23:26

Bill Sanders · Answer 4 · 2010-03-29T21:13:54.063

0

I would parse /etc/passwd for the username in question. Users may not necessarily have homedir's.

edited Mar 29 '10 at 21:13

answered Mar 29 '10 at 19:43

Bill Sanders

3

This will fail if e.g. LDAP is being used. – Ignacio Vazquez-Abrams Mar 29 '10 at 21:15
+1 for mentioning that users may not necessarily have homedirs. – Andrei Ciobanu Mar 29 '10 at 21:19
I was under the impression that not all linux flavours store user info in the /etc/passwd file... – Powertieke Mar 29 '10 at 21:28
@Powertieke: They do, if the `passwd` or `shadow` NSS databases are using `files`. See the `nsswitch.conf(5)` man page for more details. – Ignacio Vazquez-Abrams Mar 29 '10 at 21:32
The `getent`command will check all sources. `getent passwd username` – sastorsl Jun 21 '18 at 11:30

score -1 · Answer 5 · edited May 23 '17 at 11:53

-1

Similar to this answer, I would do this:

>>> import pwd
>>> 'tshepang' in [entry.pw_name for entry in pwd.getpwall()]
True

edited May 23 '17 at 11:53

Community

answered Mar 02 '13 at 00:08

tshepang

5 Answers5