Let's see if we installed Python successfully!
First check if your virtual environment is active. You should see (myenv)
in the beginning of your command line. If you don't see it, try doing conda activate <your virtuale environment name>
If it's there, we can now start Python (specifically, the Python console).
To do that, just write python:
(myenv)$ python
Python 3.8.1 (default, Dec 24 2019, 17:02:07)
[GCC 9.2.1 20191008] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>This command will print some information. In the first line, it shows which version of Python you have (you should have Python 3+). The command line starts with a >>> symbol. This way Python prompts (asks) you for instructions. This is the same as the standard command line, but instead of commands like cd or mkdir, you write Python commands.
If you have the terminal ready don't waste time! Type print("Hello, world!") in the Python terminal!
Python can work as a simple calculator:
>>> 1
1
>>> 42 + 3
45
>>> -1.1 + 12
10.9
>>> 2/3
0.6666666666666666
>>> 3*5
15
>>> 2**4
16
>>> 1e3 + 222
1222.0
>>> -8.3 + 2
-6.300000000000001
>>> 15%4
3
>>> 10_000 + 155
10155
>>> 17//3
5
>>> 2 + 3 * 4
14
>>> (2+3) * 4
20
Python prints the greater-than signs >>> and the answer by itself!
You just write number and press Enter.
Notice that commands from the standard command line do not work here, although the window looks similar:
>>> whoami
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'whoami' is not defined
This is an error message which appears every time when you do anything wrong. You will see a lot of them during the course, so look at it carefully so you recognise it later.
If you got this far, congratulations! You have installed Python and it works. You can now quit the Python console and close the command prompt. To quit, just type exit() with empty parentheses.
>>> exit()
(myenv)$
The greater-than signs >>> change back to (myenv) followed by $ or >. This tells you that you're back on the system prompt. Now commands like whoami and cd work again, but Python commands like 1 + 2 won't work. You can re-activate the Python prompt anytime you want by simply typing python - as long as you have the virtual environment active!
To quit the virtual environment, type deactivate or source deactivate (for Linux and Mac) -- this time without parentheses.
(myenv)$ deactivate
The terminal can be closed by typing exit.
$ exit
As an exercise, try to run the Python console again - open the command prompt (the terminal), then activate the virtual environment, and finally run Python.