Why do we use _ in variable names?

Question

I have seen variables like _ image and was wondering what _ meant?

Answer 1

In most languages _ is the only character allowed in variable names besides letters and numbers. Here are some common use cases:

• Separating words: some_variable
• Private variables start with underscores: _private
• Adding at the end to distinguish from a built-in name: filter_ (since filter is a built-in function)
• By itself as an unused variable during looping: [0 for _ in range(n)]

Note that some people really don't like that last use case.