How to map list in python

Question

I have 2 list below

Token_Sentence=[['This','is','a','book'],['This','is','a','cat'],['Those','are','two','books']]
Mapping=[['This',1],['is',2],['a',3],['book',4],['cat',5],['Those',6],['are',7],['two',8],['books',9]]

And I want to map Token_Sentence (convert text to index number) like this

[[1,2,3,4],[1,2,3,5],[6,7,8,9]]

and here is my code

for a in range(len(Token_Sentence)):
    for b in range(len(Token_Sentence[a])):
        for c in range(len(Mapping)):
            if Token_Sentence[a][b]==Mapping[c][0]:
                Token_Sentence[a][b]=Mapping[c][1]

But the Problem is it's take a very long time to run (my real data list is pretty large).

Is there are other ways to achieve my goal that faster and simpler than I did?

Ajax1234 · Accepted Answer · 2018-04-04 03:11:31Z

7

You can create a mapping from Mapping:

Token_Sentence=[['This','is','a','book'],['This','is','a','cat'],['Those','are','two','books']]
Mapping=[['This',1],['is',2],['a',3],['book',4],['cat',5],['Those',6],['are',7],['two',8],['books',9]]
d = dict(Mapping)
new_sentence = [[d[b] for b in i] for i in Token_Sentence]

Output:

[[1, 2, 3, 4], [1, 2, 3, 5], [6, 7, 8, 9]

edited Apr 4, 2018 at 3:11

answered Apr 4, 2018 at 3:07

Ajax1234

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2 Comments

juanpa.arrivillaga Over a year ago

Probably worth pointing out, another name for the abstract data type "dictionary" implemented by dict is called often called a map. Indeed, in Python, a dict is a mapping type

Tristan McPherson Over a year ago

I'll note that this is especially performant because dict has a lookup of O(1) instead of O(n), so overall your complexity is O(n), rather than O(n*m)

Aaditya Ura · Accepted Answer · 2018-04-04 05:56:26Z

0

Above Answer is good , Just wanted to show if you want without converting to dict :

Token_Sentence=[['This','is','a','book'],['This','is','a','cat'],['Those','are','two','books']]
Mapping=[['This',1],['is',2],['a',3],['book',4],['cat',5],['Those',6],['are',7],['two',8],['books',9]]

print([[k[1] for j in i for k in Mapping if j==k[0]] for i in Token_Sentence ])

output:

[[1, 2, 3, 4], [1, 2, 3, 5], [6, 7, 8, 9]]

answered Apr 4, 2018 at 5:56

Aaditya Ura

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