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math.ldexp

representation

The inverse of frexp: x·2**i (builds a number from its mantissa and exponent).

Syntax

math.ldexp(...)

Scaling by a power of two is exact — only the exponent moves, the significant bits stay put — which makes ldexp safer than x * 2 ** i, where a large i builds a huge intermediate integer first. Overflowing the float range raises OverflowError; going too small degrades gradually through subnormal numbers and finally to 0.0.

Examples

import math
print(math.ldexp(0.5, 3))   # → 4.0
print(math.ldexp(1, 10))   # → 1024.0
print(math.ldexp(3, -2))   # → 0.75
m, e = math.frexp(10); print(math.ldexp(m, e))   # → 10.0
print(math.ldexp(1, 5000))   # → OverflowError

See also

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