How to check immutability [duplicate]

Question 1

There are no general tests for immutability. An object is immutable only if none of its methods can mutate the underlying data.

take a look at this question

the answer says:

1) Keys must not be mutable, unless you have a user-defined class that is hashable but also mutable. That's all that's forced upon you. However, using a hashable, mutable object as a dict key might be a bad idea.

2) By not sharing values between the two dicts. It's OK to share the keys, because they must be immutable. Copying the dictionary, in the copy module sense, is definitely safe. Calling the dict constructor here works, too: b = dict(a). You could also use immutable values.

3) All built-in immutable types are hashable. All built-in mutable types are not hashable. For an object to be hashable, it must have the same hash over its entire lifetime, even if it is mutated.

4) Not that I'm aware of; I'm describing 2.x.

A type is mutable if it is not immutable. A type is immutable if it is a built-in immutable type: str, int, long, bool, float, tuple, and probably a couple others I'm forgetting. User-defined types are always mutable.

An object is mutable if it is not immutable. An object is immutable if it consists, recursively, of only immutable-typed sub-objects. Thus, a tuple of lists is mutable; you cannot replace the elements of the tuple, but you can modify them through the list interface, changing the overall data

that should answer youre question

Question 2

Do you want to check for immutability, or hashability? If you want to check whether something is hashable, hash it:

try:
    hash(thing)
except TypeError:
    print "It's unhashable."
else:
    print "It's hashable."

Hashability is usually what you want. If you want to check whether something is mutable, there's no general test.