title: what is the different between a-b ==0 and a ==b in python
body: <p>this is the code.</p>
  <pre><code>import math
  
  a = math.pow(10,100)
  b = 10 ** 100
  c = 10 ** 100
  
  print(a==b)   # false
  print(a-b==0) # true
  </code></pre>
  <p>I know the math.pow is not correct while the number is too large.  but how to understand the next point that a == b is not the same as a-b == 0 ?</p>
  <p>my python version is 3.9.6 64bit</p>