Calculate the number of primes in a range
Welcome to Code Review! Here are some suggestions.

Naming

Choose a better name than primes_2. I'm not clear on what this variable does.

Write some documentation

...in triple quotes at the top of your function. Describe its inputs and outputs.

Separate user input from processing

Put your calculation code in a separate function from your user input and output code.

Validation

If the user enters invalid input, consider looping until the input they provide is valid. Or, at least - return out of the function if it's invalid, instead of having a large else covering the rest of your code.

Increment-and-assign

Use x += 1 instead of x = x + 1.

Formatted output

Consider using this form instead:

print(f'Huh, fancy that! {len(primes)} is also a prime number!')