point from a list into a dicitonary variable

问题

Assume you have a list

a = [3,4,1]

I want with this information to point to the dictionary:

b[3][4][1]

Now, what I need is a routine. After I see the value, to read and write a value inside b's position.

I don't like to copy the variable. I want to change variable b's content directly.

回答1:

Assuming b is a nested dictionary, you could do

reduce(dict.get, a, b)

to access b[3][4][1].

For more general object types, use

reduce(operator.getitem, a, b)

Writing the value is a bit more involved:

reduce(dict.get, a[:-1], b)[a[-1]] = new_value

All this assumes you don't now the number of elements in a in advance. If you do, you can go with neves' answer.

回答2:

This would be the basic algorithm:

To get the value of an item:

mylist = [3, 4, 1]
current = mydict
for item in mylist:
    current = current[item]
print(current)

To set the value of an item:

mylist = [3, 4, 1]
newvalue = "foo"

current = mydict
for item in mylist[:-1]:
    current = current[item]
current[mylist[-1]] = newvalue

回答3:

Assuming the list length is fixed and already known

a = [3, 4, 1]
x, y, z = a
print b[x][y][z]

you can put this inside a function

来源：https://stackoverflow.com/questions/11905188/point-from-a-list-into-a-dicitonary-variable