Clamp a numeric input to a chosen interval
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Clamp a numeric input to a chosen interval
A clamp maps every value into an inclusive interval: values below the lower bound become that bound, values above the upper bound become the upper bound, and values already inside remain unchanged. This is useful when a configuration or form has already been parsed as a number but a downstream calculation accepts only a limited range.
max(lower, min(value, upper)) expresses that rule directly. The inner min caps the value at upper; the outer max then raises any remaining too-small result to lower. In this example, a requested opacity of 1.4 becomes 1.0, while 0.35 is preserved. The assertions cover all three outcomes, including the lower-bound case.
The bounds must be ordered. The helper raises ValueError instead of silently returning a surprising value when lower exceeds upper. It also assumes inputs are mutually comparable numeric values; it does not parse strings, reject NaN, or establish application-specific units. If floats can be non-finite, validate them before clamping.
min() and max() are built-in functions available in all supported Python versions. Their normal comparison behavior is documented in the Python built-in functions reference.
AI assistance disclosure: This article was drafted with AI assistance and should be adapted to the receiving application's validation rules.
def clamp(value, lower, upper):
if lower > upper:
raise ValueError("lower bound must not exceed upper bound")
return max(lower, min(value, upper))
assert clamp(-0.2, 0.0, 1.0) == 0.0
assert clamp(0.35, 0.0, 1.0) == 0.35
assert clamp(1.4, 0.0, 1.0) == 1.0
print(f"opacity={clamp(1.4, 0.0, 1.0):.1f}")opacity=1.0