Handling errors: DbdError

All errors raised by dbdreader — corrupt files, missing cache files, unreadable parameters, and so on — are reported as a single exception type: dbdreader.DbdError. Catching this one exception is therefore sufficient to guard against any error dbdreader itself might raise.

import dbdreader

try:
    dbd = dbdreader.DBD("data/amadeus-2014-204-05-000.sbd")
    t, d = dbd.get("m_depth_nonexistent")
except dbdreader.DbdError as e:
    print(f"Could not read data: {e}")

Printing (or str()-ing) a DbdError yields a human readable message describing what went wrong, for example "The requested parameter(s) was(were) not found." for the example above.

Inspecting the error in more detail

Besides the message, a DbdError carries two attributes that let you handle specific error conditions programmatically instead of parsing the message text:

• value: an integer identifying the kind of error, one of the DBD_ERROR_* constants defined in the dbdreader.dbdreader module (for example DBD_ERROR_NO_VALID_PARAMETERS or DBD_ERROR_CACHE_NOT_FOUND).

• data: an optional payload with extra information about the error. Its content depends on value; for example, when the error is caused by missing CAC cache files, data is a DbdError.MissingCacheFileData namedtuple with fields missing_cache_files and cache_dir.

import dbdreader

try:
    dbd = dbdreader.DBD("data/some_file_without_matching_cache.sbd")
except dbdreader.DbdError as e:
    if e.value == dbdreader.dbdreader.DBD_ERROR_CACHE_NOT_FOUND:
        print("Missing CAC file(s):", e.data.missing_cache_files)
        print("Looked in:", e.data.cache_dir)
    else:
        raise

Note

See Cache files and sorting filenames for how the cache directory that cache_dir refers to is determined and how to change it.