Question

I know it can denote range, but for example here [-.\d] seems like this means decimal number. What does dash symbol in front of the regex mean?
Also, why apart from [], are there () around them? What do the () mean?

Answer 1

[-.\d] finds one character that is either ([]) a dash (-), a period (.) or a number (\d).

The parentheses around mean grouping, so that the matched value can later be accessed using the group() method of the Match object.

See also the documentation of the re module.