If loop does not take correct judgement based on varible type

In the code below, if loop does not take the condition (of true) and instead goes to the elif statement. I am trying to use if statement to control what could go into a list and what can not :

average = []

def judge(result):
    try:
        float(result)
        return True
    except ValueError:
        return 'please type number'

list_in = input('Type in your number,type y when finished.\n')
judge_result = judge(list_in)
if judge_result:
    aver_trac = aver_trac + 1
    average.append(list_in)
    print('success')
elif isinstance(judge_result, str):
    print(judge_result)

However if I specify

if judge_result == True:

then this if loop will work