Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder1.news.weretis.net!feeder.erje.net!1.eu.feeder.erje.net!border1.nntp.ams1.giganews.com!nntp.giganews.com!newsfeed.xs4all.nl!newsfeed8.news.xs4all.nl!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.007 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'modify': 0.04; 'append': 0.07; 'interpreter.': 0.07; 'modifying': 0.07; 'cc:addr:python- list': 0.09; 'python': 0.10; 'itself.': 0.11; 'instead.': 0.15; 'element.': 0.16; 'prepend': 0.16; 'received:192.168.1.4': 0.16; 'sys.path': 0.16; 'wrote:': 0.16; 'element': 0.18; 'script.': 0.18; 'cc:2**0': 0.20; 'cc:addr:python.org': 0.20; 'noted': 0.22; 'trying': 0.22; 'cc:no real name:2**0': 0.22; 'insert': 0.23; 'third-party': 0.23; 'thanks,': 0.24; 'header:In-Reply-To:1': 0.24; 'script': 0.25; 'external': 0.27; 'point.': 0.27; 'fine': 0.28; 'helpful.': 0.29; 'invoke': 0.29; "i'm": 0.30; 'code': 0.30; 'convention': 0.30; 'getting': 0.33; 'url:python': 0.33; 'message- id:@gmail.com': 0.34; 'received:google.com': 0.35; 'so,': 0.35; 'path': 0.35; 'item': 0.35; 'but': 0.36; 'list,': 0.36; 'there': 0.36; 'url:org': 0.36; 'url:library': 0.36; 'pm,': 0.36; 'subject:: ': 0.37; 'method': 0.37; 'charset:us-ascii': 0.37; 'why': 0.39; 'received:192': 0.39; 'some': 0.40; 'url:3': 0.60; 'header:Message-Id:1': 0.61; 'further': 0.62; 'within': 0.64; 'managing': 0.66; 'jul': 0.72; 'url:a': 0.75; 'itself?': 0.84; 'absolutely': 0.88; 'safer': 0.91 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=content-type:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=0e/M4aA4s9nKmGYpyhBrDMTYrK17sn93Mx1j20rwGuU=; b=SXGQ4fAFjdXArjqTxx7l69gt6fRIX3TXF8OvSC9EVqFlbga9A5h7DFpVWxvKCsgj1W td8vc/jD3XeqbbalCIXGbFNHfbZRVSdXxvRtlZW8LMO8N77K/PuOdpONWy9Xt0wTdz07 VPFVQA9iG/zqrkIZ5sd1sCBzh98Xz7WGoUG+Pu7rkMBN0akQjZKDDY+9U9xN/c5yERSS tnTR6EFV9D7Y2J7dm8yYKfE+TYA46qnkxP6wolY/tMc2yXbseaSVAB6I9wRQkU1BY7Fo rte8lzYjTW4eoDazySWreV6FKSu/5bykaI2cls3DmW8Zzq3opToPuzDtk/ZpSgCn+QdP LaSw== X-Received: by 10.13.250.198 with SMTP id k189mr32973703ywf.46.1438023371719; Mon, 27 Jul 2015 11:56:11 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 6.6 \(1510\)) Subject: Re: sys path modification From: Cem Karan In-Reply-To: Date: Mon, 27 Jul 2015 14:56:07 -0400 Cc: python-list@python.org Content-Transfer-Encoding: quoted-printable References: To: neubyr X-Mailer: Apple Mail (2.1510) X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.20+ Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.python Message-ID: Lines: 32 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1438023374 news.xs4all.nl 2847 [2001:888:2000:d::a6]:53583 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:94672 On Jul 27, 2015, at 1:24 PM, neubyr wrote: >=20 > I am trying to understand sys.path working and best practices for = managing it within a program or script. Is it fine to modify sys.path = using sys.path.insert(0, EXT_MODULES_DIR)? One stackoverflow answer - = http://stackoverflow.com/a/10097543 - suggests that it may break = external 3'rd party code as by convention first item of sys.path list, = path[0], is the directory containing the script that was used to invoke = the Python interpreter. So what are best practices to prepend sys.path = in the program itself? Any further elaboration would be helpful.=20 Why are you trying to modify sys.path? I'm not judging, there are many = good reasons to do so, but there may be safer ways of getting the effect = you want that don't rely on modifying sys.path. One simple method is to = modify PYTHONPATH = (https://docs.python.org/3/using/cmdline.html#envvar-PYTHONPATH) = instead. In order of preference: 1) Append to sys.path. This will cause you the fewest headaches. 2) If you absolutely have to insert into the list, insert after the = first element. As you noted from SO, and noted in the docs = (https://docs.python.org/3/library/sys.html#sys.path), the first element = of sys.path is the path to the directory of the script itself. If you = modify this, you **will** break third-party code at some point. =20 Thanks, Cem Karan=