你好，我有一个错误，这是告诉我变量定义，但它的定义行以上
我做错了什么？
我的代码：

a = open("dialogs/dialogs.txt").read().splitlines()
def parse(string):
    string = string.lower().split()
    s1 = ""
    for l in string:
        s1+=l[0]
    return s1
def get_database(data,database,database1):
    for c,i in enumerate(database):
        if data in i:
            mp004 = c
    return database1[mp004]

ques = []
anws = []
for c,i in enumerate(a):
    try:
        m = i.split("\t")
        ques.append(parse(m[0]))
        anws.append(m[1])
    except:
        pass
    print(f"Trained {c}/{len(a)-1}            ",end="\r")
    
print()
while True:
    p = input("> ")
    print(get_database(p,ques,anws))

错误信息：

Traceback (most recent call last):
  File "/data/user/0/ru.iiec.pydroid3/files/accomp_files/iiec_run/iiec_run.py", line 31, in <module>
    start(fakepyfile,mainpyfile)
  File "/data/user/0/ru.iiec.pydroid3/files/accomp_files/iiec_run/iiec_run.py", line 30, in start
    exec(open(mainpyfile).read(),  __main__.__dict__)
  File "<string>", line 28, in <module>
  File "<string>", line 12, in get_database
UnboundLocalError: local variable 'mp004' referenced before assignment

我到底做错了什么？