can't round number

Question

I am trying to create a prime factor searcher. However when I try to round a number in line 3 it keeps telling me that it can not round a str. And when I replace a by float(a) or
int(a) it will both of the times say float object cannot be interpreted as integer. Does anyone know how this comes and how I can solve this?

import math
a=input()
b=round(math.sqrt(float(a)),0)
primes=[]
for num in range(2,b):
prime = True
for i in range(2,num):
if (num%i==0):
prime = False
if prime:
primes.append(num)
for i in primes:
if int(a)%int(i)==0:
print(i)
print(int(int(a)/int(i)))
break

Answer 1

Your error is to get a 'b' variable of type float, even you round it to an integer... You must change the type of var 'b' to be integer type ( not just mathematically ) to be compatible with the range() function ^^

b=int(math.sqrt(float(a)),0)