Question

Problem: I have to check that the a returned value is a Python dictionary.

Q1. Which of these options is the proper way to do this?

type(x) == dict

type(x) == type(dict)

isinstance(d, dict)

Then there are the other variants using is operator instead of ==.

Q2. Many people say that checking the type of an object is generally a bad practice, but regarding to my initial problem, do I have any other choice?

Answer 1

Q1. Which of these options is the proper way to do this?

Don’t waste time on type checking.

It’s error-prone because it’s based on assumptions.

Q2. … do I have any other choice?

Yes do this.

try:
    x.the_dict_operation()
except TypeError:
    # x was not the expected type for the operation
    raise # or whatever.

In most cases, this amounts to “do nothing”.

Just write the code. If “somehow” a malicious sociopath uses the wrong type, it will just crash like it’s supposed to.