In this interactive terminal, we’ll walk through opening Python for the first time. For simplicity, we’ll do this on the command line. First, find your respective terminal application. After opening, type on the command line
$ python --version
Python 2.7.9
This command will let you know which version of python you are running, if any. If the version number is less than 3.2, as above, you may need to use the command
$ python3 --version
Python 3.4.2
If you do not have python 3.2 or greater installed, take a look at the introduction page.
Next, since python is installed, let’s try to open it. Type
$ python3
You should see something like the following
Python 3.4.2 (default, Jan 12 2015, 11:38:40)
[GCC 4.9.2 20141224 (prerelease)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>
Great! You’ve opened python for the first time! Now how the heck do you get out of it? You can either type exit() or use the key command Ctrl-D to exit.
Now let’s try typing some things in the python command line. The >>> means the
interpreter is ready for the next command. How about some simple math? Try
typing the following, then pressing enter.
>>> 1+1
>>> 300+1.
>>> 30/3
>>> 30./3.
>>> 2*3
>>> 2**3
>>> 20. % 3You’ll notice that without a decimal at the end of a number, python
automatically treats the number as an integer. We’ll get to this in the next
tutorial. Also, the % sign means modulo, which is always a good tool for
counting.
Now, try the following:
>>> print("hello world")
>>> print("SPAM")I think you get the hang of it. Let’s try something a bit different. Exit python to the terminal, and open a new file called MyExample.py using your favorite editor. In this file, write the following lines:
#!/bin/python3
print('Green Eggs and Spam')
print(2**100)
Now, on the command line, type
python3 MyExample.py
What happened? You just wrote your first script!