Choose a random dimer

Question

Good evening! Given the dictionary with the probabilities of finding each letter in the first and second place:

profile = {'A': [0.5, 0.1], 'C': [0.3, 0.2], 'G': [0.2, 0.4], 'T': [0.0, 0.3]}

I need, based on their probabilities, to randomly choose a dimer ('AA', 'AC', etc.)

I can get randomly selected non-integer number:

 random.uniform(0, 1)

Then for the first letter of a dimer, I can write the following:

 0 to 0.5 —-> 'A', 0.5 to 0.8 —-> 'C', 0.8 to 1 —-> 'G',

Considering that I cannot use the 'ACTG' keys directly, because the keys may have other names, I need to write a function that selects a random dimer based on the probabilities of each letter on each of the two places. Any ideas? I have been sitting on this task for quite a long time.

Community spirit ♦ one · Answer 1 · 2016-12-04T07:38:42

The choice of the first and second letters is completely independent:

 letters = list(profile) dimer = ''.join([letters[weighted_choice(weights)] for weights in zip(*profile.values())])

where zip(*matrix) transposes the matrix and weighed_choice(weights) selects a random index according to the given weights for the current position. See the weighted_choice () discussion in the related question .

Xander xander 10.5k 2 eleven 33 · Answer 2 · 2016-12-03T20:08:23

 from random import random def dimer(profile): # Перевожу данные в структуру с фиксированным порядком элементов data = [(k, v[0], v[1]) for k, v in profile.items()] # Первый символ rnd1 = random() acc1 = 0 for d in data: acc1 += d[1] if acc1 > rnd1: first = d[0] break # Второй символ rnd2 = random() acc2 = 0 for d in data: acc2 += d[2] if acc2 > rnd2: second = d[0] break return first + second

The function works correctly if the sum of the probabilities in the source data is one.

He takes into account the order of the elements of the dictionary.
The order of the elements in the data will be different for different launches.
@kff, no, his order is preserved only at the stage where he builds the interval of the probability distribution.
After the random choice has been made, the order has ceased to influence anything.

Choose a random dimer

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