Python 检查键是否在字典中定义
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Python check that key is defined in dictionary
提问by user10756
How to check that the key is defined in dictionary in python?
如何检查密钥是否在python的字典中定义？
a={}
...
if 'a contains key b':
a[b] = a[b]+1
else
a[b]=1
采纳答案by Martijn Pieters
Use the inoperator:
使用in运算符：
if b in a:
Demo:
演示：
>>> a = {'foo': 1, 'bar': 2}
>>> 'foo' in a
True
>>> 'spam' in a
False
You really want to start reading the Python tutorial, the section on dictionariescovers this very subject.
你真的想开始阅读 Python 教程，词典部分涵盖了这个主题。
回答by bruno desthuilliers
Its syntax is if key in dict::
它的语法是if key in dict:：
if "b" in a:
a["b"] += 1
else:
a["b"] = 1
Now you may want to look at collections.defaultdictand (for the above case) collections.Counter.
现在您可能想要查看collections.defaultdict和（对于上述情况）collections.Counter。
回答by Ishaan
if b in a:
a[b]+=1
else:
a[b]=1
回答by Srinivasreddy Jakkireddy
a = {'foo': 1, 'bar': 2}
if a.has_key('foo'):
a['foo']+=1
else:
a['foo']=1
回答by Ranvijay Sachan
parsedData=[]
dataRow={}
if not any(d['url'] == dataRow['url'] for d in self.parsedData):
self.parsedData.append(dataRow)
