# Default user agent, unless instructed by the user to change it.
import os
import random


USER_AGENT = 'Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0)'

# Load the list of valid user agents from the install folder.
# The search order is:
#   * user_agents.txt.gz
#   * user_agents.txt
#   * default user agent
try:
    install_folder = os.path.abspath(os.path.split(__file__)[0])
    try:
        user_agents_file = os.path.join(install_folder, 'user_agents.txt.gz')
        import gzip
        fp = gzip.open(user_agents_file, 'rb')
        try:
            user_agents_list = [_.strip() for _ in fp.readlines()]
        finally:
            fp.close()
            del fp
    except Exception:
        user_agents_file = os.path.join(install_folder, 'user_agents.txt')
        with open(user_agents_file) as fp:
            user_agents_list = [_.strip() for _ in fp.readlines()]
except Exception:
    user_agents_list = [USER_AGENT]


# Get a random user agent.
def get_random_user_agent():
    """
    Get a random user agent string.

    :rtype: str
    :return: Random user agent string.
    """
    return random.choice(user_agents_list)

def main():
    print(get_random_user_agent())

if __name__ == "__main__":
    main()