[SOLVED] error while trying to install a package using the python-apt API

Issue

I found a code which i need. It is from this link : How to install a package using the python-apt API

#!/usr/bin/env python
# aptinstall.py

import apt
import sys

pkg_name = "libjs-yui-doc"

cache = apt.cache.Cache()
cache.update()   # error is in this line

pkg = cache[pkg_name]
if pkg.is_installed:
    print "{pkg_name} already installed".format(pkg_name=pkg_name)
else:
    pkg.mark_install()

    try:
        cache.commit()
    except Exception, arg:
        print >> sys.stderr, "Sorry, package installation failed [{err}]".format(err=str(arg))

However i can't make it work. I searched about the problem on the web. It is said that there should be no package manager,apt,pip etc active in order to work with this code. However, no package manager,apt,pip etc. is open in my computer. I thought that when computer starts, some package manager can be active. So i typed

 ps -aux 

in terminal and look at the active processes, but i didn't see any active process related to package manager(i'm not %100 sure about this, because any process i don't know can be related to package manager.But how could i know it?) To sum up,i started the computer and opened only terminal. Then i typed python aptinstall.py and hit enter. I take the following error :

Traceback (most recent call last):
  File "aptinstall.py", line 7, in <module>
    cache.update()
  File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 397, in update
    raise LockFailedException("Failed to lock %s" % lockfile)
apt.cache.LockFailedException: Failed to lock /var/lib/apt/lists/lock

I delete the lock by giving the command in terminal : sudo rm /var/lib/dpkg/lock It didn't work too.

How can i solve this problem? Any idea will be appreciated.

Solution

There are three different reasons which cause this error.

1 - As i mentioned earlier, if any package manager is runnning(for example;pip,apt-get,synaptic,etc), it gives the error.

2 - If you are using your ubuntu in a virtual machine, this causes the same error.

3 - If you are running your program without root privileges, this causes the same error. For example ,if you are running your program with "python aptinstall.py" you get the error, running the program with "sudo python aptinstall.py" is the correct one.

Answered By - oiyio