Python Interview Questions and Answers: Singleton, Lambda, Type Conversion, Functions, Memory Management, and More

1. Singleton pattern in Python can be implemented using a metaclass or a decorator. Example code shows a Singleton metaclass and a decorator approach.

2. Lambda functions are anonymous one‑line functions that can take any number of arguments and return the result of a single expression. Examples demonstrate basic usage and immediate invocation.

3. Type conversion functions such as int(), float(), and str() convert values between types, with examples of successful and failing conversions.

4. Functions are defined with the def keyword, must have a name starting with a letter, and use indentation to delimit the body. An example of an addition function is provided.

5. Memory management in Python is handled by the interpreter, relieving developers from manual allocation.

6. To iterate a sequence in reverse, use list.reverse() for lists or a reversed index loop for other sequences.

7. Converting between tuples and lists is done with tuple(seq) and list(seq), preserving element order.

8. Removing duplicate elements from a list can be done by sorting the list and deleting consecutive duplicates, as shown in the code example.

9. File operations: delete a file with os.remove() or os.unlink(); copy a file with shutil.copyfile().

10. Generating random numbers uses the random module, e.g., random.random() returns a float in [0,1).

11. Sending email via SMTP can be done with the smtplib library; a sample script reads a message from stdin and sends it.

12. Object copying uses copy.copy() or copy.deepcopy(); dictionaries have a copy() method.

13. Static analysis tools such as PyChecker and Pylint help find bugs and enforce coding standards.

14. Global variables inside a function are declared with the global statement.

15. In regular expressions, <.*> is greedy, while <.*?> is non‑greedy, affecting how HTML tags are matched.

16. re.match() checks only at the start of a string, whereas re.search() scans the whole string for a match.

17. The except clause catches exceptions; examples show catching all exceptions versus specific ones like IOError.