Is "I don’t suppose" used as a question? What kind of expression is it? and is this a frequently used expression?
Answer from a Native speaker
To "suppose" something means to "think", "assume" or "guess". So the expression "I don't suppose" means "I don't think" or "I'm guessing/assuming I can't". "I don't suppose" is used to introduce a question when you think you already know something is untrue, but you want to ask just in case it is true. Ex: You don't suppose the dog ate our sandwiches, do you? Ex: I don't suppose you have his phone number? This expression is still heard today but it is not very common because it is formal. A more common expression heard today with the same meaning is "you don't happen to". Ex: You don't happen to think the cat ran away? Ex: You don't happen to have her address, do you?