How to register and than search a value in CSV file?

Question

I'm trying to register an user and then read the data I just appended. It looks like the csv file is appending the value, but it's not saving it. But this is awkward, because I used the "with open" function at the "registered" function.

def is_registered(ID): #OK
    df = read_any_csv(users_path)
    x = df.loc[df["ID"] == ID]
    if x.empty:
        return False
    else:
        return True

#faz o cadastro do usuario
def register(ID): #OK
        x = str(input("Escreva seu nome:  "))        
        name = x.title()
        section = int(input("Digite seu setor(111/112/113): "))
        data = [name,ID,section]
        with open (users_path,'a') as file:
            writer = csv.writer(file)
            writer.writerow(data)
def start():
#Se o usuario estiver registrado, da as boas vindas a ele, caso nao, registra ele e depois da as boas vindas
    if is_registered(ID) == True: #OK
        current_user = users_df.loc[users_df["ID"] == ID]
        name = current_user["NAME"]
        name2 =(name.to_string(index=False))
        section = current_user["SECTION"]
        print(f"Ola, {name2}, bem vindo ao programa de treinamento Mercedes Benz Brasil!\n")
        videos = videos_to_watch(section)
        print("Esses sao os videos que faltam serem assistidos:\n")
        print(*videos,sep = '\n')
    else: #OK
        register(ID)
        users_df.to_csv("Users.csv",index = False)    
        current_user = users_df.loc[users_df["ID"] == ID]     
        print(current_user) 

But the csv can't find the data, the result that I got is that:

Digite o ID: aaaaa
Escreva seu nome:  leo
Digite seu setor(111/112/113): 113
Empty DataFrame
Columns: [NAME, ID, SECTION]
Index: []

What I actually want is:

Digite o ID: 5DBEF04B
Escreva seu nome:  Raul Lopes Camina
Digite seu setor(111/112/113): 113
Ola, Raul Lopes Camina, bem vindo ao programa de treinamento Mercedes Benz Brasil!

Answer 1

You write new data to file but this can't change original users_df and you would have to read it again (instead of write again)

    register(ID)

    users_df = pd.read_csv("Users.csv")  # <-- read instead of write

    current_user = users_df.loc[users_df["ID"] == ID]     

    print(current_user) 

---

Or you should first add to users_df and later save it with to_csv - and then you don't have to read it again.

def register(ID):  # OK
    global users_df  # need it to add to external variable
    
    name = str(input("Escreva seu nome:  "))        
    name = name.title()
    section = int(input("Digite seu setor(111/112/113): "))

    data = pd.DataFrame({'NAME': [name], 'ID': [ID], 'SECTION': [section]})
    
    users_df = pd.concat([users_df, data])   # <-- add to original `users_df`

    users_df.to_csv("Users.csv", index=False)    

and later

    register(ID)

    # without `to_csv()` and `read_csv()`

    current_user = users_df.loc[users_df["ID"] == ID]     

    print(current_user)