Replace string with numeric values based on dictionary

Question

I have a list of strings like the following:

strings = ["acbd", "abc", "acbde", "abc"]

And a dictionary containing numeric representations of each character:

dict_ = {"a":[0.4, 0.3, 0.8, -0.1], "b":[1.5, -1.6, 1.2], "c":[7.4, 4.3], "d":[4.23, 0.5, 0.9, 0.5, 1.7], "e":[1.5, 8.1]}

How can I get a numeric representation for each string in strings? For example, for "acbd", I want a concatenated list of the constituent characters in order: [0.4, 0.3, 0.8, -0.1, 7.4, 4.3, 1.5, -1.6, 1.2, 4.23, 0.5, 0.9, 0.5, 1.7]. I want an output with a list of lists, with each list being a numeric representation of the string.

What is the most efficient way of doing this also?

My real data has over 100000 strings and all 26 characters.

Answer 1

Here's one solution using itertools.chain and a list comprehension.

This has no optimisation for repeated strings. I suggest you test with your data to see if performance is adequate.

from itertools import chain

res = [list(chain.from_iterable(map(dict_.get, i))) for i in strings]

print(res)

[[0.4, 0.3, 0.8, -0.1, 7.4, 4.3, 1.5, -1.6, 1.2, 4.23, 0.5, 0.9, 0.5, 1.7],
 [0.4, 0.3, 0.8, -0.1, 1.5, -1.6, 1.2, 7.4, 4.3],
 [0.4, 0.3, 0.8, -0.1, 7.4, 4.3, 1.5, -1.6, 1.2, 4.23, 0.5, 0.9, 0.5, 1.7, 1.5, 8.1],
 [0.4, 0.3, 0.8, -0.1, 1.5, -1.6, 1.2, 7.4, 4.3]]