Randomizing the upper and lowercase of a string

Is there a more efficient / smarter way of randomizing the uppercasing of letters in a string ? Like this:

input_string = "this is my input string"
for i in range(10):
    output_string = ""
    for letter in input_string.lower():
        if (random.randint(0,100))%2 == 0:
            output_string += letter
        else:
            output_string += letter.upper()
    print(output_string)

Output:

thiS iS MY iNPUt strInG
tHiS IS My iNPut STRInG
THiS IS mY Input sTRINg
This IS my INput STRING
ThIS is my INpUt strIng
tHIs is My INpuT STRInG
tHIs IS MY inPUt striNg
THis is my inPUT sTRiNg
thiS IS mY iNPUT strIng
THiS is MY inpUT sTRing