Function _decimal_lshift_exact

Lib/_pydecimal.py:5653–5672

Given integers n and e, return n * 10**e if it's an integer, else None. The computation is designed to avoid computing large powers of 10 unnecessarily. >>> _decimal_lshift_exact(3, 4) 30000 >>> _decimal_lshift_exact(300, -999999999) # returns None

(n, e)

_nbits = int.bit_length

def _decimal_lshift_exact(n, e):
    """ Given integers n and e, return n * 10**e if it's an integer, else None.

    The computation is designed to avoid computing large powers of 10
    unnecessarily.

    >>> _decimal_lshift_exact(3, 4)
    30000
    >>> _decimal_lshift_exact(300, -999999999)  # returns None

    """
    if n == 0:
        return 0
    elif e >= 0:
        return n * 10**e
    else:
        # val_n = largest power of 10 dividing n.
        str_n = str(abs(n))
        val_n = len(str_n) - len(str_n.rstrip('0'))
        return None if val_n < -e else n // 10**-e

def _sqrt_nearest(n, a):
    """Closest integer to the square root of the positive integer n.  a is