What issues are present in the following Python code?

The code contains several problems:

1. Operator mapping is incorrect: the subtraction operator is represented by '.' instead of '-'. This will raise a KeyError or produce wrong results.
2. The print statement uses the string "12+4=" but calls calc(12,4,'*'), which multiplies instead of adding. The label does not match the operation.
3. The default argument for add_to_inventory is a mutable list. Each call shares the same list, so items accumulate across calls. This is a classic Python pitfall. The function should use None as the default and create a new list inside the function.
4. The print statements for add_to_inventory use a leading space before the string, which may be unintended.
5. The code lacks error handling for division by zero; it raises ZeroDivisionError but does not provide a message.

Fixes:

• Use '-' for subtraction.
• Align the print label with the operation.
• Change the default argument to None and initialize a new list inside the function.
• Optionally add a message for ZeroDivisionError.

Complexity: The functions run in O(1) time; add_to_inventory is O(1) per call, but the list grows with each call.