My attempt at FizzBuzz (Python 3)
It's a good attempt, it reads easily and I like that you nested the FizzBuzz check within Fizz branch. 

This doesn't look like most of the code you see in the wild, though, so a good exercise would be to extract a function for the FizzBuzz logic that is independent from the loop over numbers.

def get_fizzbuzz(num:int) -&gt; str:
    result = ""
    # fizzbuzz logic
    if num % 3 == 0:
        if num % 5 == 0:
            result = "FizzBuzz"
        # ...
    return result


You could even make it more flexible by optionally allowing different numbers to be entered instead of 3 and 5, while still using 3 and 5 as default values, like so:

 def get_fizzbuzz(num:int, fizz:int = 3, buzz:int = 5) -&gt; str:
    result = ""
    # fizzbuzz logic
    if num % fizz == 0:
        if num % buzz == 0:
            result = "FizzBuzz"
        # ...
    return result   


Then you can just call the function in a loop using the default values:

for num in range(1, 101):
    print(get_fizzbuzz(num))


Or alternatively with different values for fizz and buzz:

for num in range(1, 101):
    print(get_fizzbuzz(num, 5, 7))


That will help you make your code more modular.

Note that I used Python 3's type hints in the function definition, which are completely optional but can make the code more clear, as well as provide static code analysis with certain tools.