C:> py -m pip install pandas %= one of Python on the system =%
C:> py -2 -m pip install pandas %= one of Python 2 on the system =%
C:> py -2.7 -m pip install pandas %= only for Python 2.7 =%
C:> py -3 -m pip install pandas %= one of Python 3 on the system =%
C:> py -3.6 -m pip install pandas %= only for Python 3.6 =%