how to call all python terminals at once code example

Example 1: run python file using python code

exec(open('file.py').read())

Example 2: how to run a python script

# Save the script in a file with .py extension
# run the script using the below command
python fileName.py

Example 3: to run python script in terminal i want to type python insted of python3

$ python --version
Python 2.7.6
$ python3 --version
Python 3.4.3
$ alias python=python3
$ python --version
Python 3.4.3