Python 字典推导式中的条件表达式
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Conditional expressions in Python Dictionary comprehensions
提问by user462455
a = {"hello" : "world", "cat":"bat"}
# Trying to achieve this
# Form a new dictionary only with keys with "hello" and their values
b = {"hello" : "world"}
# This didn't work
b = dict( (key, value) if key == "hello" for (key, value) in a.items())
Any suggestions on how to include a conditional expression in dictionary comprehension to decide if key, value tuple should be included in the new dictionary
关于如何在字典理解中包含条件表达式以决定键、值元组是否应包含在新字典中的任何建议
采纳答案by Rohit Jain
Move the ifat the end:
移动if最后：
b = dict( (key, value) for (key, value) in a.items() if key == "hello" )
You can even use dict-comprehension(dict(...)is not one, you are just using the dictfactory over a generator expression):
您甚至可以使用dict-comprehension（dict(...)不是一个，您只是dict在生成器表达式上使用工厂）：
b = { key: value for key, value in a.items() if key == "hello" }
回答by falsetru
You don't need to use dictionary comprehension:
您不需要使用字典理解：
>>> a = {"hello" : "world", "cat":"bat"}
>>> b = {"hello": a["hello"]}
>>> b
{'hello': 'world'}
and dict(...)is not dictionary comprehension.
并且dict(...)不是字典理解。
