的Python：使用namedtuple._replace具有可变的字段名

Question

我可以参考使用的变量的namedtuple fieldame？

from collections import namedtuple
import random 

Prize = namedtuple("Prize", ["left", "right"]) 

this_prize = Prize("FirstPrize", "SecondPrize")

if random.random() > .5:
    choice = "left"
else:
    choice = "right"

#retrieve the value of "left" or "right" depending on the choice

print "You won", getattr(this_prize,choice)

#replace the value of "left" or "right" depending on the choice

this_prize._replace(choice  = "Yay") #this doesn't work

print this_prize

Answer 1

元组是不可变的，因此是NamedTuples。他们不应该被改变！

this_prize._replace(choice = "Yay")呼叫_replace与关键字参数"choice"。它不使用choice作为变量，并尝试通过choice的名称来代替字段。

this_prize._replace(**{choice : "Yay"} )将使用任何choice是作为字段名

_replace返回一个新NamedTuple。你需要reasign它：this_prize = this_prize._replace(**{choice : "Yay"} )

只需使用一个字典或写一个普通的类代替！

Answer 2

>>> choice = 'left'
>>> this_prize._replace(**{choice: 'Yay'})         # you need to assign this to this_prize if you want
Prize(left='Yay', right='SecondPrize')
>>> this_prize
Prize(left='FirstPrize', right='SecondPrize')         # doesn't modify this_prize in place