Python: round(2.5) = 2?!FREE

Python rounds exact halves to the nearest EVEN number. See it happen, then use school rounding when you need it.

# round(2.5) = 2 ?!  — Python rounds exact halves to the nearest EVEN number
# ("banker's rounding"), so ties don't all drift upwards.

print("round(2.5) =", round(2.5))   # 2  ?!
print("round(3.5) =", round(3.5))   # 4
print("round(0.5) =", round(0.5))   # 0
print("round(1.5) =", round(1.5))   # 2

# School rounding (halves always go up) for positive numbers:
def school_round(x):
    return int(x + 0.5)

print("school_round(2.5) =", school_round(2.5))   # 3 ✓

# Try it: change 2.5 to 2.51 — no longer a tie, so it rounds to 3.

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