I am trying to run a small python code (which requries pytz and some other packages) on a aws ec2 instance. When I tried to install pytz, I got some errors:

```
[ec2-user@ip-172-31-28-178 ~]$ pip install pytz
Collecting pytz
  Using cached pytz-2016.7-py2.py3-none-any.whl
Installing collected packages: pytz
Exception:
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/pip/basecommand.py", line 215, in main
    status = self.run(options, args)
  File "/usr/local/lib/python2.7/site-packages/pip/commands/install.py", line 342, in run
    prefix=options.prefix_path,
  File "/usr/local/lib/python2.7/site-packages/pip/req/req_set.py", line 784, in install
    **kwargs
  File "/usr/local/lib/python2.7/site-packages/pip/req/req_install.py", line 851, in install
    self.move_wheel_files(self.source_dir, root=root, prefix=prefix)
  File "/usr/local/lib/python2.7/site-packages/pip/req/req_install.py", line 1064, in move_wheel_files
    isolated=self.isolated,
  File "/usr/local/lib/python2.7/site-packages/pip/wheel.py", line 345, in move_wheel_files
    clobber(source, lib_dir, True)
  File "/usr/local/lib/python2.7/site-packages/pip/wheel.py", line 316, in clobber
    ensure_dir(destdir)
  File "/usr/local/lib/python2.7/site-packages/pip/utils/__init__.py", line 83,  in ensure_dir
    os.makedirs(path)
  File "/usr/lib64/python2.7/os.py", line 157, in makedirs
    mkdir(name, mode)
OSError: [Errno 13] Permission denied: '/usr/local/lib/python2.7/site-packages/pytz-2016.7.dist-info'

```

I followed the accepted answer of [this topic](https://stackoverflow.com/questions/31512422/pip-install-r-oserror-errno-13-permission-denied) but got another error:

`sudo:pip: command not found`

Then I found out it might be because the path setting is wrong 
(according to [this page](https://askubuntu.com/questions/378349/when-using-sudo-to-run-pip-pip-command-not-found-but-its-installed). But I could not manage to `Just add ~/.local/bin to your path` as suggested by the second answer.

Can someone show me how to add the bin to my path? I have no idea. 

And some more info:

```
[ec2-user@ip-172-31-28-178 ug]$ echo $PATH
/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/opt/aws/bin:/home/ec2-user/.local/bin:/home/ec2-user/bin
[ec2-user@ip-172-31-28-178 ug]$ which pip
/usr/local/bin/pip
[ec2-user@ip-172-31-28-178 ug]$

```