In Python please!

Write a function brackets (expr) that takes a string consisting only of the symbols (, ), 1, >, [ and ] and analyzes the string to make sure that the brackets are all "balanced" (matched) properly. For example the strings O' and ( [(([))])' contain balanced brackets, whereas [ O O', )' and ' (' are unbalanced. We refer to (, f and [ as "left brackets", and), ) and ] as "right brackets" The basic algorithm to implement works like this: input: a string S output: a list L for each character in S if the character is a left bracket