Hi, I have just produced the following log in IDLE (admittedly, in Python 2.7.10 and, yes I know that it has been superseded).
It appears to show a precision tail-off as the supplied float gets bigger. I have two questions: 1. Is there a straightforward explanation for this or is it a bug? 2. Is the same behaviour exhibited in Python 3.x? For your information, the first 20 significant figures of the cube root in question are: 49793385921817447440 Stephen Tucker. ---------------------------------------------- >>> 123.456789 ** (1.0 / 3.0) 4.979338592181744 >>> 123456.789 ** (1.0 / 3.0) 49.79338592181744 >>> 123456789. ** (1.0 / 3.0) 497.9338592181743 >>> 123456789000. ** (1.0 / 3.0) 4979.338592181743 >>> 123456789000000. ** (1.0 / 3.0) 49793.38592181742 >>> 123456789000000000. ** (1.0 / 3.0) 497933.8592181741 >>> 123456789000000000000. ** (1.0 / 3.0) 4979338.59218174 >>> 123456789000000000000000. ** (1.0 / 3.0) 49793385.9218174 >>> 123456789000000000000000000. ** (1.0 / 3.0) 497933859.2181739 >>> 123456789000000000000000000000. ** (1.0 / 3.0) 4979338592.181739 >>> 123456789000000000000000000000000. ** (1.0 / 3.0) 49793385921.81738 >>> 123456789000000000000000000000000000. ** (1.0 / 3.0) 497933859218.1737 >>> 123456789000000000000000000000000000000. ** (1.0 / 3.0) 4979338592181.736 >>> 123456789000000000000000000000000000000000. ** (1.0 / 3.0) 49793385921817.36 >>> 123456789000000000000000000000000000000000000. ** (1.0 / 3.0) 497933859218173.56 >>> 123456789000000000000000000000000000000000000000. ** (1.0 / 3.0) 4979338592181735.0 >>> 123456789000000000000000000000000000000000000000000. ** (1.0 / 3.0) 4.979338592181734e+16 >>> 123456789000000000000000000000000000000000000000000000. ** (1.0 / 3.0) 4.979338592181734e+17 >>> 123456789000000000000000000000000000000000000000000000000. ** (1.0 / 3.0) 4.979338592181733e+18 >>> 123456789000000000000000000000000000000000000000000000000000. ** (1.0 / 3.0) 4.979338592181732e+19 >>> 123456789000000000000000000000000000000000000000000000000000000. ** (1.0 / 3.0) 4.9793385921817313e+20 ---------------------------------------------- -- https://mail.python.org/mailman/listinfo/python-list
