What does += mean in Python?

Question

I see code like this for example in Python:

    if cnt > 0 and len(aStr) > 1:
        while cnt > 0:                  
            aStr = aStr[1:]+a         


        

Answer 1

a += b

is in this case the same as

a = a + b

In this case cnt += 1 means that cnt is increased by one.

Note that the code you pasted will loop indefinitely if cnt > 0 and len(aStr) > 1.

Edit: quote Carl Meyer: ``[..] the answer is misleadingly mostly correct. There is a subtle but very significant difference between + and +=, see Bastien's answer.''.