Question

For example,
The function could be something like def RandABCD(n, .25, .34, .25, .25):

Where n is the length of the string to be generated and the following numbers are the desired probabilities of A, B, C, D.

I would imagine this is quite simple, however i am having trouble creating a working program. Any help would be greatly appreciated.

Answer 1

Thank you all for your help, I was able to figure something out, mostly with this info.
For my particular need, I did something like this:

import random
#Create a function to randomize a given string
def makerandom(seq):
    return ''.join(random.sample(seq, len(seq)))
def randomDNA(n, probA=0.25, probC=0.25, probG=0.25, probT=0.25):
    notrandom=''
    A=int(n*probA)
    C=int(n*probC)
    T=int(n*probT)
    G=int(n*probG)

#The remainder part here is used to make sure all n are used, as one cannot
#have half an A for example.
    remainder=''
    for i in range(0, n-(A+G+C+T)):
        ramainder+=random.choice("ATGC")
    notrandom=notrandom+ 'A'*A+ 'C'*C+ 'G'*G+ 'T'*T + remainder
    return makerandom(notrandom)