Path: csiph.com!news.swapon.de!fu-berlin.de!uni-berlin.de!not-for-mail
From: Tim Chase <python.list@tim.thechases.com>
Newsgroups: comp.lang.python
Subject: Re: Trailing zeros of 100!
Date: Sat, 2 Jan 2016 10:33:01 -0600
Lines: 28
Message-ID: <mailman.171.1451752514.11925.python-list@python.org>
References: <52ccbc4b-616b-4186-8802-97aaa5b0d9af@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
X-Trace: news.uni-berlin.de 8nbFMpt6YRRqCjGw97M7Mw3z8dMV0qZxSefmk8skkLVg==
Return-Path: <python.list@tim.thechases.com>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.002
X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'trailing': 0.07; "'0',": 0.09; 'zeros': 0.09; 'python': 0.10; '-tkc': 0.16; 'failed.': 0.16; 'from:addr:python.list': 0.16; 'from:addr:tim.thechases.com': 0.16; 'from:name:tim chase': 0.16; 'itertools': 0.16; 'lambda': 0.16; 'received:io': 0.16; 'received:psf.io': 0.16; 'wrote:': 0.16; 'module,': 0.18; 'math': 0.20; 'trying': 0.22; 'help.': 0.23; 'import': 0.24; 'header:In- Reply-To:1': 0.24; "i'm": 0.30; 'received:184': 0.30; 'but': 0.36; 'skip:i 20': 0.36; 'to:addr:python-list': 0.36; 'subject:: ': 0.37; 'received:10': 0.37; 'charset:us-ascii': 0.37; 'to:addr:python.org': 0.40; 'easy': 0.60; 'email addr:gmail.com': 0.62
X-Sender-Id: wwwh|x-authuser|tim@thechases.com
X-Sender-Id: wwwh|x-authuser|tim@thechases.com
X-MC-Relay: Neutral
X-MailChannels-SenderId: wwwh|x-authuser|tim@thechases.com
X-MailChannels-Auth-Id: wwwh
X-MC-Loop-Signature: 1451752510046:728422456
X-MC-Ingress-Time: 1451752510046
In-Reply-To: <52ccbc4b-616b-4186-8802-97aaa5b0d9af@googlegroups.com>
X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.25; x86_64-pc-linux-gnu)
X-AuthUser: tim@thechases.com
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.20+
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <https://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive: <http://mail.python.org/pipermail/python-list/>
List-Post: <mailto:python-list@python.org>
List-Help: <mailto:python-list-request@python.org?subject=help>
List-Subscribe: <https://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Xref: csiph.com comp.lang.python:101159

On 2016-01-02 03:49, katye2007@gmail.com wrote:
> I'm trying to write a python program to find how many trailing
> zeros are in 100! (factorial of 100). I used factorial from the
> math module, but my efforts to continue failed. Please help.

Pretty easy to do with strings:

  from math import factorial
  n = factorial(100)
  s = str(n)
  print(len(s) - len(s.rstrip('0')))

or count them:

  from itertools import takewhile
  sum(1 for _ in takewhile(lambda c: c == '0', reversed(s)))

or mathematically:

  sum(1 for _ in itertools.takewhile(
    lambda x: n % (10**x) == 0,
    itertools.count(1)))

-tkc