Which type of quotation marks are the best or the right ones to use, the single or the double ones? I tend to use double quotation marks because I find those easier to find and use on my Scandinavian keyboard (they do not share the same key) but I would love to hear what you guys suggest.

For example in Python:
print("Hello world!")
print('Hello world!')

Quotation marks, single or double? Which ones do you use and why?