如何检查字典中的列表是否为键？

Question

我有这样的字典：

a = {'values': [{'silver': '10'}, {'gold': '50'}]}

现在，我想检查键“ silver”是否在字典中：

if 'silver' in a['values']:

但是我收到错误消息：

NameError: name 'silver' is not defined

那么我如何在python中实现呢？

Answer 1

您可以使用any。

if any('silver' in d for d in a['values']):
   # do stuff

Answer 2

# Notice that a['values'] is a list of dictionaries.
>>> a = {'values': [{'silver': '10'}, {'gold': '50'}]}

# Therefore, it makes sense that 'silver' is not inside a['values'].
>>> 'silver' in a['values']
False

# What is inside is {'silver': '10'}.
>>> a['values']
[{'silver': '10'}, {'gold': '50'}]

---

# To find the matching key, you could use the filter function.
>>> matches = filter(lambda x: 'silver' in x.keys(), a['values'])

# 'next' allows you to view the matches the filter found. 
>>> next(matches)
{'silver': '10'}

# 'any' allows you to check if there is any matches given the filter. 
>>> any(matches):
True

• filter()
• next()
• any()

Answer 3

您可以尝试以下方法：

if 'silver' in a['values'][0].keys():

Answer 4

如果要采用列表插值方法，可以将字典列表展平为键列表，如下所示：

In: [key for pair in a['values'] for key in pair.keys()]
Out: ['silver', 'gold']

然后：

In: 'silver' in [key for pair in a['values'] for key in pair.keys()]
Out: True

基于this answer展平列表列表。