sequence of bases with equal probability

Question

I want to create a sequence of the bases (A,T,G,C) which all appear at the same probability. The sequence should have a variable length n. Could you help me?

Answer 1

python has a module named random to choose randomly from a sample.

import random
n = 5 # set n
random_list = random.choices(range(4), k=n)
dic = {0:"A", 1:"C", 2:"G", 3:"T"}
bases_list = [dic[v] for v in random_list]
seq = ""
for item in bases_list:
    seq += item

At first you create a list of n random numbers, all in range [0,3]. Then you use a dictionary to replace numbers with strings representing bases.

Now when we have a list, I just put them all together in one string to create one sequence. That what the last three lines are doing.

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