[Tutor] Rounding a float to n significant digits

[Dick Moores]

I just dug this Tim Smith creation out of the Tutor archive.

def round_to_n(x, n):
        """
        Rounds float x to n significant digits, in scientific notation.
        Written by Tim Peters. See his Tutor list post of 7/3/04 at
        http://mail.python.org/pipermail/tutor/2004-July/030324.html
        """
        if n < 1:
                raise ValueError("number of significant digits must be >= 1")
        return "%.*e" % (n-1, x)

Thought others might find it of use.

Dick Moores

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