from datetime import datetime


def days_diff(start_date: datetime, end_date: datetime) -> int:
    """Calculates diff in days between start date and end date"""
    diff = start_date - end_date
    return diff.days


def get_tag_value_by_key(tags: list, tag_name: str) -> str:
    """return tag value or empty string in tag doesn't exist"""
    value = ""
    for tag in tags:
        if tag["Key"] == tag_name:
            value = tag["Value"]

    return value