"Longest Substring Without Repeating Characters" in Python
Nice solution, please find a few thoughts below:


Do you need to wrap it in class for leetcode? It's unnecessary otherwise.
Function names use snake_case and not camelCase, check PEP8 for more details. Hence it would be length_of_longest_substring.
Do not use dict as a variable name, it is already built-in to construct dictionaries.
I think a for-loop would be preferable over a while-loop in this case, it's more straightforward, less clunky, and easier to understand.
You update curr_length, but never actually use it to determine your max_length.
The docstring should come right after the class Solution and before the first function, and no line should be longer than 79 characters. Moreover, you seem to not have pasted the entire docstrings, it just ends mid-sentence.