将字符串元素中的1s翻转为0，反之亦然

Question

I'm writing a simple genetic algorithm and the mutation operator requires me to randomly flip a "gene" (ie: a single char in a string) with a certain probability.

This is an example of the list I need to go through flipping randomly each character:

a = ['0010010', '0011101', '1101101', '0100110', '1010100', '1000111', '1001110', '0010011', '0011111', '0001001', '0101000', '1010010', '1110000', '0000001', '1100111', '1001100', '1000001', '1001010']

I loop through each character in each element of the list to check if I have to flip it like so:

for elem in a:
    for char in elem:
        r = random.random()
        if r<prob:
            # Flip the char.
            f_char = 1-int(char)
            # Replace the new flipped char in the element?

(where prob is a fixed float [0,1] )

I'm not sure how I could update the elem with the new flipped character in the case I have to. I'd also need this process to run as fast as possible since my actual list is somewhat large.

Answer 1

Two choices:

One, you can use a list of integers instead of a string. Then, mutate them in-place:

a = [[0, 0, 1, 0, 0, 1, 0], [0, 0, 1, 1, 1, 0, 1]]
for elem in a:
    for i, bit in enumerate(elem):
        r = random.random()
        if r < prob:
            elem[i] = 1 - bit

Two, you can still use strings, but then you have to replace the entire string every time you want to change one character in it, because Python strings are immutable. Best way is using a generator comprehension, as in inspectorG4dget's answer:

a = ['0010010', '0011101']
for i, elem in enumerate(a):
    a[i] = ''.join(str(1 - int(char)) if random.random() < prob else char
                   for char in elem)

Answer 2

Strings are immutable, so you'll have to replace the entire chromosome in your list of chromosomes, when you mutate even one gene in the chromosome. So try this:

for i,elem in enumerate(a):
    a[i] = ''.join(char if random.random()>prob else str(1-int(char)) for char in elem)