当值是python中的列表列表时，如何将值添加到字典中

Question

I am trying to build a dictionary, such that for each key the value is a list of lists. There is a loop in my code thats runs on some list of keys, and if the key not in the dictionary, i add the key to the the dictionary with some value. I get into truble when the key is in the dictionary- i cannot add to it another list.

here is example for what i tried:

dict={}

dict[x]=[[f,g],[y,e,j]...]
# i tried this:
dict[x]+= [l,k,n]

dict[x].append([l,k,n])

#i expected this:

dict[x] = [[f,g],[y,e,j], ... ,[l,k,n]]

Answer 1

This seems to work for me:

a = [1,2,3]
b = [4,5,6]
d = {}
d['ab'] = [a, b]
d['ab'].append([7,8,9])

Note that d['ab'] += [0,0,0] (as an example) does an extend rather than a append . If you want to use += then you should wrap the value in a list. eg:

d['ab'] += [[0,0,0]]