290. Word Pattern

class Solution:
    def wordPattern(self, pattern, str):
        """
        :type pattern: str
        :type str: str
        :rtype: bool
        """
        a_dict = {}
        new_list = str.split()
        if len(pattern) != len(new_list):
            return False
        else:
            for i in range(len(pattern)):
                if pattern[i] in a_dict:
                    if a_dict[pattern[i]] != new_list[i]:
                        return False
                else:
                    if new_list[i] in a_dict.values():
                        return False
                    else:
                        a_dict[pattern[i]] = new_list[i]
        return True