On Windows system, if you install Python3 via
Anaconda. Under Anaconda root directory,
there is a directory named Scripts, in which pip.exe, pip3.exe and
pip3.6.exe all exist. When we want to install a package, a natural question
arises, is there any difference if I use pip install PACKAGE or pip3 install PACKAGE?
On Windows#
The three executables have exactly the same file size and file last-mod time:

If you show their version information, the output is also exactly the same. On my system, the output is:
pip 18.1 from d:\anaconda\lib\site-packages\pip (python 3.6)
So, on Windows, the three executables have no difference.
What about Linux?#
On Linux, the default python is usually Python 2. If you are a system
administrator and install python2-pip package, you will see that pip and
pip2 under /usr/bin are the same. If you also installed python3-pip,
there will an executable named pip3 under /usr/bin. Under this situation,
pip and pip2 is used for installing Python 2.X packages and pip3 is used
for Python 3.
You can also verify this by using pip[3] --version. On my system (Ubuntu on
Windows), the result of pip --version is:
pip 9.0.1 from /usr/lib/python2.7/dist-packages (python 2.7)
, while the output of pip3 --version is;
pip 9.0.1 from /usr/lib/python3/dist-packages (python 3.6)
It is clear that they are different.