I want to check whether python 3 is installed on my Ubuntu. I'm using this script:

```
#!/usr/bin/env sh

#install firefox if does not exist
if ! command -v python3 >/dev/null 2>&1
        then
                echo "not installed"
        else
                echo "installed"
fi

```

When I run this script, the output is `installed`, but when I check my python using `python --version`, I get this output:

```
Python 2.7.17

```

Which, as far as I know, means that the latest version of python on my Ubuntu is 2.7 not 3.x. What's wrong?

The output of `command -v python3; echo $?`:

```
/usr/bin/python3
0

```

The output of `ls -l /usr/bin/python3`:

```
lrwxrwxrwx 1 root root 9 Nov 14 09:13 /usr/bin/python3 -> python3.7

```

The output of `ls -l /usr/bin/python3.7`:

```
-rwxr-xr-x 2 root root 5102632 Oct 27 11:43 /usr/bin/python3.7

```

The output of `which python`:

```
/usr/bin/python

```

The output of `ls -l /usr/bin/python`:

```
lrwxrwxrwx 1 root root 7 Jan 19 08:04 /usr/bin/python -> python2

```

The output of `ls -l /usr/bin/python2`:

```
lrwxrwxrwx 1 root root 9 Jan 19 08:04 /usr/bin/python2 -> python2.7

```

Also I have another Ubuntu on a separate VM, the output of `python --version`, returns `command 'python' not found`, but when I execute the above commands for this VM as well, it returns similar responses (indicating that python is installed).