`decode()` error message uses broken format string

The TypeError in decode() uses "multihash should be bytes, not {}" without an f-string prefix, so the {} is printed literally instead of being replaced with the actual type.

Problem

In multihash/multihash.py, the decode() function:

def decode(multihash):
    if not isinstance(multihash, bytes):
        raise TypeError("multihash should be bytes, not {}", type(multihash))
        #                     ↑ Missing 'f' prefix — {} is literal

When called with a non-bytes argument:

>>> decode("not bytes")
TypeError: multihash should be bytes, not {}
# Expected: TypeError: multihash should be bytes, not <class 'str'>

Proposed Solution

Fix the f-string:

def decode(multihash):
    if not isinstance(multihash, bytes):
        raise TypeError(f"multihash should be bytes, not {type(multihash)}")

Add a test:

def test_decode_type_error_message():
    with pytest.raises(TypeError, match="multihash should be bytes, not"):
        decode("not bytes")

Related

• File: multihash/multihash.py, decode() function

Open multihash/multihash.py and inspect the decode() type check. Confirm the current TypeError prints the placeholder literally, then add the proposed regression test for a non-bytes argument. The work is done when the message includes the actual argument type and the test passes.