import pandas as pd

hd = pd.read_csv('HD.dat', sep='|', header=None, dtype=str, encoding='latin-1', on_bad_lines='skip', usecols=[1, 4])
hd.columns = ['usi', 'call_sign']
hd['call_sign'] = hd['call_sign'].str.strip()

usi = hd.loc[hd['call_sign'] == 'WQSY442', 'usi'].iloc[0]
print("unique_system_identifier:", usi)

lo = pd.read_csv('LO.dat', sep='|', header=None, dtype=str, encoding='latin-1', on_bad_lines='skip')
row = lo[lo[1] == usi]
print(row.to_string())