如何在Python字典中访问列表内的元素？

Question

我有一个函数返回一个JSON格式的数据集。以下是一个示例：

[{u'category': [u'Transfer', u'Withdrawal', u'ATM'], u'category_id': u'21012002', u'_account': u'XARE85EJqKsjxLp6XR8ocg8VakrkXpTXmRdOo', u'name': u'ATM Withdrawal', u'amount': 200, u'meta': {u'location': {u'city': u'San Francisco', u'state': u'CA'}}, u'date': u'2014-07-21', u'score': {u'location': {u'city': 1, u'state': 1}, u'name': 1}, u'_id': u'0AZ0De04KqsreDgVwM1RSRYjyd8yXxSDQ8Zxn', u'type': {u'primary': u'special'}, u'pending': False}] 

for trans in foodie_data:
            print 'Name={},Amount={},Date={}, Categories ={}\n'.format(trans['name'],trans['amount'],trans['date'],trans['category'])

这段脚本会输出：

Name=ATM Withdrawal,Amount=200,Date=2014-07-21,Categories=[u'Transfer', u'Withdrawal', u'ATM']

我希望它返回一个字符串而不是列表的类别：

Name=ATM Withdrawal,Amount=200,Date=2014-07-21,Categories='Transfer, Withdrawal,ATM']

什么是最有效的方法？

- Mitch

---

', '.join(trans['category']) 的意思是什么？ - Shashank

Answer 1

您可以将类别元素组合起来：

>>> categories = [u'Transfer', u'Withdrawal', u'ATM']
>>> ",".join(categories)
u'Transfer,Withdrawal,ATM'

在打印输出时，使用它来代替：

",".join(trans['category'])

- JuniorCompressor

Answer 2

您的代码中应该只需要两个快速修复即可解决问题

1. Join the list returned by trans['category'] separated by comma such that it is a string rather than a string representation of list.

2. Quote the format specifier for category i.e. Categories =\'{}\'

   for trans in foodie_data:
       print 'Name={},Amount={},Date={}, Categories =\'{}\'\n'.format(
       trans['name'],
       trans['amount'],
       trans['date'],
       ', '.join(trans['category']))
   

- Abhijit

Answer 3

你也可以直接使用字典和 str.format 来访问其余的值：

for trans in foodie_data:
    print "Name={name},Amount={amount},Date={date}," \
       "Categories='{}'\n".format(",".join(trans["category"]),**trans)


 Name=ATM Withdrawal,Amount=200,Date=2014-07-21,Categories='Transfer,Withdrawal,ATM'

- Padraic Cunningham