Python 就地修改字典值
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Modify dict values inplace
提问by Qortex
I would like to apply a function to values of a dictinplace in the dict(like mapin a functional programming setting).
我想将函数应用于dictinplace 中的值dict（例如map在函数式编程设置中）。
Let's say I have this dict:
假设我有这个dict：
d = { 'a':2, 'b':3 }
I want to apply the function divide by 2.0to all values of the dict, leading to:
我想将该函数divide by 2.0应用于 dict 的所有值，导致：
d = { 'a':1., 'b':1.5 }
What is the simplest way to do that?
最简单的方法是什么？
I use Python 3.
我使用Python 3。
Edit:A one-liner would be nice. The divide by 2is just an example, I need the function to be a parameter.
编辑：单线会很好。这divide by 2只是一个例子，我需要函数作为参数。
采纳答案by John La Rooy
You may find multiply is still faster than dividing
你可能会发现乘法仍然比除法快
d2 = {k: v * 0.5 for k, v in d.items()}
For an inplace version
对于就地版本
d.update((k, v * 0.5) for k,v in d.items())
For the general case
对于一般情况
def f(x)
"""Divide the parameter by 2"""
return x / 2.0
d2 = {k: f(v) for k, v in d.items()}
回答by jamylak
>>> d = { 'a': 2, 'b': 3 }
>>> {k: v / 2.0 for k, v in d.items()}
{'a': 1.0, 'b': 1.5}
回答by Brendan Long
You can loop through the keys and update them:
您可以遍历键并更新它们：
for key, value in d.items():
d[key] = value / 2
回答by Ishpeck
Should work for you:
应该为你工作：
>>> d = {'a':2.0, 'b':3.0}
>>> for x in d:
... d[x]/=2
...
>>> d
{'a': 1.0, 'b': 1.5}
