Random String Generator (Python)

import random

def randomString(length):
    lower = 'a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z'.split(',')
    caps = 'A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z'.split(',')
    numbers = '0,1,2,3,4,5,6,7,8,9'.split(',')
    special =  '!,@,#,$,%,^,&,*,(,),-,_,~,=,+'.split(',')
    try:
        float(length)
    except ValueError:
        length = 32
    x = array_merge(array_merge(numbers, special), array_merge(lower, caps))
    random.shuffle(x)
    str = ''
    for ind in range(0, length):
        str += x[ random.choice(range(len(x))) ]
    return str

def array_merge(first_array, second_array):
    if isinstance(first_array, list) and isinstance(second_array, list):
        return first_array + second_array

    elif isinstance(first_array, dict) and isinstance(second_array, dict):
        return dict(list(first_array.items()) + list(second_array.items()))

    elif isinstance(first_array , set) and isinstance(second_array , set):
        return first_array.union(second_array)

    return False

length = 30
String = randomString(length)
print(String)