Path: csiph.com!usenet.pasdenom.info!aioe.org!news.stack.nl!newsfeed.xs4all.nl!newsfeed3a.news.xs4all.nl!xs4all!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 0.001 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'syntax': 0.04; 'subject:Question': 0.07; 'function,': 0.09; 'parameter': 0.09; 'creates': 0.14; '(note': 0.16; 'called,': 0.16; "didn't,": 0.16; 'expects': 0.16; 'expression,': 0.16; 'finney': 0.16; 'from:addr:mrabarnett.plus.com': 0.16; 'from:addr:python': 0.16; 'from:name:mrab': 0.16; 'function;': 0.16; 'helps.': 0.16; 'lambda': 0.16; 'lambda:': 0.16; 'message- id:@mrabarnett.plus.com': 0.16; 'positional': 0.16; 'received:192.168.1.4': 0.16; 'sugar': 0.16; 'syntactic': 0.16; 'wrote:': 0.18; 'variable': 0.18; 'examples': 0.20; 'starts': 0.20; 'creating': 0.23; 'header:User-Agent:1': 0.23; "i've": 0.25; 'header:In-Reply-To:1': 0.27; 'function': 0.29; 'appreciated.': 0.29; "i'm": 0.30; 'changed.': 0.31; 'parameters.': 0.31; 'writes:': 0.31; 'allows': 0.31; 'trouble': 0.34; 'useful': 0.36; 'ben': 0.38; 'to:addr:python-list': 0.38; 'to:addr:python.org': 0.39; 'changed': 0.39; 'skip:x 10': 0.40; 'expression': 0.60; 'hope': 0.61; 'new': 0.61; 'name': 0.63; 'different': 0.65; 'skip:\xe2 10': 0.65; '8bit%:40': 0.68; 'default': 0.69; '8bit%:43': 0.74; 'special': 0.74 X-CM-Score: 0.00 X-CNFS-Analysis: v=2.1 cv=ZuVjKrLG c=1 sm=1 tr=0 a=0nF1XD0wxitMEM03M9B4ZQ==:117 a=0nF1XD0wxitMEM03M9B4ZQ==:17 a=0Bzu9jTXAAAA:8 a=xSRs65CQCjkA:10 a=IkcTkHD0fZMA:10 a=EBOSESyhAAAA:8 a=pGLkceISAAAA:8 a=mEsJUVyd_1CdlE8V5xEA:9 a=QEXdDO2ut3YA:10 X-AUTH: mrabarnett:2500 Date: Tue, 09 Dec 2014 01:40:42 +0000 From: MRAB User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: python-list@python.org Subject: Re: Question on lambdas References: <85oarditil.fsf@benfinney.id.au> In-Reply-To: <85oarditil.fsf@benfinney.id.au> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.15 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: 43 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1418089246 news.xs4all.nl 2845 [2001:888:2000:d::a6]:57882 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:82168 On 2014-12-08 23:58, Ben Finney wrote: > memilanuk writes: > >> What I'm having trouble finding a concrete answer to is the difference >> between: > > (Note that where you write “some_func” the syntax requires an > expression, not a function. I've changed your examples to be clear). > >> lambda: some_expr > > This creates a new function which expects zero parameters. The function, > when called, will return the value of ‘some_expr’. > >> lambda x: some_expr > > This creates a new function which expects one positional parameter named > ‘x’. The function, when called, will return the value of ‘some_expr’. > >> lambda x=some_value: some_expr > > This creates a new function which expects one parameter named ‘x’, which > parameter has a default value of ‘some_value’. The function, when > called, will return the value of ‘some_expr’. > This is useful when you want to 'capture' the current value of 'some_value' to be passed to some_expr; if you didn't, then some_expr would be using the value of 'some_value' at the time it was called, which might be different if some variable it used had been changed. >> Any help would be greatly appreciated. > > Hope that helps. > > It's best to remember that ‘lambda’ is syntactic sugar for creating a > function; the things it creates are not special in any way, they are > normal functions, not “lambdas”. > > What is different is that the function starts with no name bound to it, > and the syntax allows only a single expression as the body of the > function. >