for nth square root: use math.sqrt n times for example >>> import math >>> num = 625 >>> how_many_sqrt = 2 >>> for i in range(how_many_sqrt): .. num = math.sqrt(num) .. >>> num 5.0
all comparisons work fine for arbitrary floating point numbers... For readability print them with required precision. for example >>> a = .2 >>> b = .4 >>> b = b/2 >>> a == b True >>> a, b (0.20000000000000001, 0.20000000000000001) >>> '%.2f' % a, '%.2f' % b ('0.20', '0.20') >>> thx. Edwin -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of CNiall Sent: Sunday, August 03, 2008 10:03 AM To: python-list@python.org Subject: Decimals not equalling themselves (e.g. 0.2 = 0.2000000001) I am very new to Python (I started learning it just yesterday), but I have encountered a problem. I want to make a simple script that calculates the n-th root of a given number (e.g. 4th root of 625--obviously five, but it's just an example :P), and because there is no nth-root function in Python I will do this with something like x**(1/n). However, with some, but not all, decimals, they do not seem to 'equal themselves'. This is probably a bad way of expressing what I mean, so I'll give an example: >>> 0.5 0.5 >>> 0.25 0.25 >>> 0.125 0.125 >>> 0.2 0.20000000000000001 >>> 0.33 0.33000000000000002 As you can see, the last two decimals are very slightly inaccurate. However, it appears that when n in 1/n is a power of two, the decimal does not get 'thrown off'. How might I make Python recognise 0.2 as 0.2 and not 0.20000000000000001? This discrepancy is very minor, but it makes the whole n-th root calculator inaccurate. :\ -- http://mail.python.org/mailman/listinfo/python-list The information contained in this message and any attachment may be proprietary, confidential, and privileged or subject to the work product doctrine and thus protected from disclosure. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please notify me immediately by replying to this message and deleting it and all copies and backups thereof. Thank you. -- http://mail.python.org/mailman/listinfo/python-list