python: search for a value in a dictionary

gistfile1

def find_key(dic, val):
    """return the key of dictionary dic given the value"""
    return [k for k, v in symbol_dic.iteritems() if v == val][0]
{
    1: '128.0.0.0', 2: '192.0.0.0',
    3: '224.0.0.0', 4: '240.0.0.0',
    5: '248.0.0.0', 6: '252.0.0.0',
    7: '254.0.0.0', 8: '255.0.0.0',
    9: '255.128.0.0', 10: '255.192.0.0',
    11: '255.224.0.0', 12: '255.240.0.0',
    13: '255.248.0.0', 14: '255.252.0.0',
    15: '255.254.0.0', 16: '255.255.0.0',
    17: '255.255.128.0', 18: '255.255.192.0',
    19: '255.255.224.0', 20: '255.255.240.0',
    21: '255.255.248.0', 22: '255.255.252.0',
    23: '255.255.254.0', 24: '255.255.255.0',
    25: '255.255.255.128', 26: '255.255.255.192',
    27: '255.255.255.224', 28: '255.255.255.240',
    29: '255.255.255.248', 30: '255.255.255.252',
    31: '255.255.255.254', 32: '255.255.255.255'
}