Python Forum

I am writing a method and it outputs unexpected results. It is supposed to break up some strings and create lists from them. Yet the lists don't contain everything I expected.

Here is my code:

def get_group_users():
    f = open('group.example', 'r')          #f is file

    users = []                              #obvious
    for l in f:                                     
        g = l.split(':')                    #g is group
        if (g[0] == "users"):
            for ul in g[3]:                 #ul is userline
                gu = ul.split(',')          #gu is groupuser
                for u in gu:                #u is user
                    users.append(u)

    return users

This is the group.example file...

users:x:100:kintaro,john,autossh,test
portage:x:250:portage

This is the output which I did not expect...

>>> import shadowssh
>>> shadowssh.get_group_users()
['k', 'i', 'n', 't', 'a', 'r', 'o', '', '', 'j', 'o', 'h', 'n', '', '', 'a', 'u', 't', 'o', 's', 's', 'h', '', '', 't', 'e', 's', 't', '\n']

The output I want...

['kintaro', 'john', 'autossh', 'test']

replace lines 8 to 11 with

users.extend(g[3].split(','))

as a side note - using one-letter names is bad, use descriptive names

That did not work, and line 8 is an important conditional so that it avoids the group portage in my example.

At line 7 your group is parsed into g as a list of strings such as ['users', 'x', '100', 'kintaro,john,autossh,test']

Line 8 is

            for ul in g[3]:                 #ul is userline

This sets ul to the elements of g[3] one at a time. Since g[3] is a string, it sets ul to each of the characters. You want to split g[3], not loop on it.

Thanks for helping me figure that out...

def get_group_users():
    f = open('group.example', 'r')

    users = []
    for l in f:
        g = l.split(':')
        if (g[0] == "users"):
            for u in g[3].split(','):
                users.append(u)

    return users

line 8 is the root of your problem
g[3] is a string and you iterate over string. so u is each char in that string. then you try to split single char at ',' (line 9)

what i suggest:

def get_group_users():
    f = open('group.example', 'r')          #f is file
 
    users = []                              #obvious
    for l in f:                                     
        g = l.strip().split(':')                    #g is group
        if (g[0] == "users"):
            users.extend(g[3].split(','))
    return users

print(get_group_users())

Output:
['kintaro', 'john', 'autossh', 'test']

Now, what I would do, to make better code

def get_group_users(file_name):
    users = []
    with open(file_name, 'r') as f:
        for line in f:
            if line.startswith('users'):
                *_, group_users = line.strip().split(':')
                users.extend(group_users.split(','))
    return users

print(get_group_users('group.example'))

Output:
['kintaro', 'john', 'autossh', 'test']

note the use of strip() in order to remove the new-line '\n' at the end of last element