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.