Question

我有一本字典，我尝试使用以下代码将数据写入currency.csv文件：字典的代码是

def _fetch_currencies():
     response =urllib.request.urlopen('http://www.maths.manchester.ac.uk/~vsego/python/currencies.json')
     html = response.read().decode("utf-8")

     currencies = json.loads(html)
     pprint(currencies)

def _save_currencies(currencies):
    with open(('currencies.csv'), 'wt') as my_csv:
        csv_writer = csv.writer(my_csv, delimiter=',')
        csv_writer.writerow(["code","name"])  
        for key,value in currencies.items(): 
            csv_writer.writerow([key,value])

 _save_currencies(_fetch_currencies())

当我返回代码时，我收到错误消息

'AttributeError: 'NoneType' object has no attribute 'items''

如何解决此错误？

Answer 1

您需要返回_fetch_currencies()：

def _fetch_currencies():
     response =urllib.request.urlopen('http://www.maths.manchester.ac.uk/~vsego/python/currencies.json')
     html = response.read().decode("utf-8")
     return json.loads(html) # <- return

您不会返回任何值，因此默认情况下，python返回None，因此当您将_fetch_currencies()传递给_save_currencies时，您正在传递None。

您也可以传递dict.items并致电csv.writerows：

def _save_currencies(currencies):
    with open(('currencies.csv'), 'wt') as my_csv:
        csv_writer = csv.writer(my_csv, delimiter=',')
        csv_writer.writerow(["code","name"])
        csv_writer.writerows(currencies.items())

Answer 2

错误是因为您从没有任何字典的字典中请求密钥。原因是_fetch_currencies（）没有return语句。

def _fetch_currencies():
     response =urllib.request.urlopen('http://www.maths.manchester.ac.uk/~vsego/python/currencies.json')
     html = response.read().decode("utf-8")

     currencies = json.loads(html)
     return currencies

无论如何，这应该有效：

currencies = {}
for key,value in currencies.items(): 
    print key, value

这不起作用：

currencies = None
for key,value in currencies.items(): 
    print key, value

将字典保存为CSV文件

2 个答案: