未定義變量的錯誤，雖然它在功能上

Question

def append_customer(file_variable, fields): 
""" 
------------------------------------------------------- 
Appends a customer record to a sequential file. 
------------------------------------------------------- 
Preconditions: 
    file_variable - the file to search (file) 
    fields - data to append to the file (list) 
Postconditions: 
    The data in fields are appended to file_variable. 
------------------------------------------------------- 
""" 
if os.path.exists(file_variable) == True: 
    file = open(file_variable, "w", encoding="utf-8") 
    file.seek(0) 
    print("{0}".format(fields), file=file_variable) 
file.close() 
return 

的已定義這是一個功能我寫的數據添加到文件中，唯一的錯誤在於顯然是「file_variable未定義」 ......即使它清楚地由函數定義。我不知道爲什麼會發生此錯誤。

Answer 1

這似乎更接近你想要什麼：

def append_customer(file_variable, fields): 
    """ 
    ------------------------------------------------------- 
    Appends a customer record to a sequential file. 
    ------------------------------------------------------- 
    Preconditions: 
     file_variable - the file to search (file) 
     fields - data to append to the file (list) 
    Postconditions: 
     The data in fields are appended to file_variable. 
    ------------------------------------------------------- 
    """ 
    if os.path.exists(file_variable): 
     with open(file_variable, "a", encoding="utf-8") as fobj: 
      fobj.write("{0}\n".format(fields)) 

您需要縮進功能體。

如果你想打開一個現有的文件進行追加，你需要使用'a'這意味着「開放的寫作，追加到文件的末尾，如果它存在」。 with語句打開該文件並在離開縮進時關閉它。