Python Quirks and Tricky Behaviors: 10 Quiz Questions with Explanations

01. round() function – The code print(round(9/2)) print(round(7/2)) print(round(3/2)) produces 4, 4, 2 because Python uses banker's rounding, rounding half values to the nearest even integer.

02. Instance attribute lookup – The snippet class A: ans = 9 def __init__(self): self.answer = 10 self.__add__ = lambda x, y: x.answer + y def __add__(self, y): return self.answer - y print(A() + 4) outputs 6 . Python first searches the instance for the attribute, then the class; the custom __add__ defined on the instance is ignored, so the class method runs, computing 10‑4 .

03. max() with -0.0 – The code print(max(-0.0, 0.0)) returns -0.0 because -0.0 and 0.0 compare equal, and max returns the first occurrence.

04. Lazy operators (all / any) – The snippet print(all([])) print(any([])) produces True, False . all returns True for an empty iterable (no false element found), while any returns False (no true element found).

05. Negative string multiplication – The code print("Can you give 50 claps to this story?" * (-1)) outputs an empty string because a negative repeat count is treated as zero.

06. Everything is an object – The snippet print(isinstance(object, type)) print(isinstance(type, object)) print(isinstance(type, type)) print(isinstance(object, object)) prints True, True, True, True since in Python all types are objects and type itself is an instance of type .

07. sum() with non‑numeric start – The code print(sum("")) print(sum("", [])) print(sum("", {})) yields 0, [], {} because the empty string is treated as an empty iterable and the start value is returned unchanged.

08. Lazy class example – The snippet class follow: def func(self): return follow() a = follow() follow = int print(a.func()) outputs 0 . The name follow is rebound to int only after the class is defined; the method returns a new int instance.

09. Summing imaginary parts – The code print(sum([a.imag for a in [0, 5, 10e9, float('inf'), float('nan')]])) produces 0.0 because all numbers have an imaginary part of zero.

10. Floating‑point precision limits – The snippet a = (1 << 53) + 1 print(a + 1.0 > a) raises an error in the original text, but the explanation shows that converting the large integer to float loses precision, making the comparison evaluate to False .

These ten puzzles illustrate subtle Python behaviors that can trap developers, helping them understand the language’s internal mechanics and avoid unexpected bugs.