我们可以用一系列正则表达式来解决这个问题：

import re

def ruby_hash_to_json(input_str):
    input_str = input_str.replace('=>', ':')
    input_str = input_str.replace(':nil', ':null')  # JSON uses null, not None

    # Remove weekday from date string and add quotes around date
    input_str = re.sub(r'\w+, (\d{2} \w{3} \d{4})', r'"\1"', input_str)

    # Convert Ruby's symbols (words preceded by a colon) into valid JSON keys (quoted words)
    # This handles symbols both at the beginning of the string and in other positions.
    input_str = re.sub(r'({|, ):(\w+)', r'\1"\2"', input_str)

    return input_str