python - Python 字典理解中的条件表达式

Question

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())

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

Answer 1

将 if 移到末尾:

b = dict( (key, value) for (key, value) in a.items() if key == "hello" )

您甚至可以使用 dict-comprehension(dict(...) 不是一个，您只是在使用 dict 工厂一个生成器表达式):

b = { key: value for key, value in a.items() if key == "hello" }