Why is the command 'sudo pip uninstall' not working?

Question

When I type the following command in Ubuntu, it is showing all list of python packages:

$  sudo pip list
adium-theme-ubuntu (0.3.2)
apt-xapian-index (0.44)
apturl (0.5.1ubuntu3)
argparse (1.2.1)
BeautifulSoup (3.2.0)
Brlapi (0.5.6)
bzr (2.5.1)
chardet (2.0.1)
command-not-found (0.2.44)
dirspec (3.0.0)
distribute (0.7.3)
dnspython (1.9.4)
docutils (0.8.1)
duplicity (0.6.18)
gdata (2.0.14)
GnuPGInterface (0.3.2)
httplib2 (0.7.2)
jockey (0.9.7)
louis (2.3.0)
mercurial (2.0.2)
nvidia-common (0.0.0)
onboard (0.97.1)
oneconf (0.2.8.1)
PAM (0.4.2)
paramiko (1.7.7.1)
pexpect (2.3)
pip (1.4.1)
piston-mini-client (0.7.2)
Pmw (1.3.2)
psutil (0.4.1)
psycopg2 (2.4.5)
PyChart (1.39)
pycrypto (2.4.1)
pycups (1.9.61)
pycurl (7.19.0)
pydot (1.0.2)
pyinotify (0.9.2)
pyOpenSSL (0.12)
pyparsing (1.5.2)
pyserial (2.5)
pysmbc (1.0.13)
python-apt (0.8.3ubuntu7.2)
python-ldap (2.3.13)
python-openid (2.2.5)
python-virtkey (0.60.0)
pyxdg (0.19)
PyYAML (3.10)
reportlab (2.5)
sessioninstaller (0.0.0)
setuptools (0.8b2)
simplejson (2.3.2)
system-service (0.1.6)
Twisted-Core (11.1.0)
Twisted-Names (11.1.0)
Twisted-Web (11.1.0)
ubuntuone-couch (0.3.0)
ubuntuone-installer (3.0.2)
ubuntuone-storage-protocol (3.0.2)
ufw (0.31.1-1)
unattended-upgrades (0.1)
unittest2 (0.5.1)
unity-lens-video (0.3.5)
unity-scope-video-remote (0.3.5)
usb-creator (0.2.23)
uTidylib (0.2)
wsgiref (0.1.2)
xdiagnose (2.5.3)
xkit (0.0.0)
xlwt (0.7.2)
ZSI (2.1-a1)

When I import a particular package, it is working perfect:

$ sudo python
Python 2.7.3 (default, Sep 26 2013, 20:08:41) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import argparse
>>> 

But when I try to uninstall particular package, it throws an error like this:

$  sudo pip uninstall argparse
Can't uninstall 'argparse'. No files were found to uninstall.

Why I am facing above problem?

Answer 1

If you haven't used pip to install argparse (unlikely, as it is python core library), you don't use pip to uninstall it.

Answer 2

For not-too-old python versions (python 2.7+), argparse is part of the python distribution, and therefore you can't uninstall it easily (and it's not a good idea to do this anyway).

As per the comments, there is a possibility to do this using easy_install -m and then deleting the .egg file.

Also afaik, you can't generally uninstall packages with pip that you haven't installed with pip. Use whatever you installed a package with, to uninstall it. Your package manager (apt-get) is one option here.