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Re: pylint woes

From DFS <nospam@dfs.com>
Newsgroups comp.lang.python
Subject Re: pylint woes
Date 2016-05-07 22:15 -0400
Organization A noiseless patient Spider
Message-ID <ngm79s$d60$1@dont-email.me> (permalink)
References (1 earlier) <CAPTjJmr7A+UH7Wye05_T5WV0kG=DQUrOF2Mc8-uGQ26HKAoCMg@mail.gmail.com> <mailman.457.1462640479.32212.python-list@python.org> <ngm3qs$73r$1@dont-email.me> <CAPTjJmqBzdVqY+3nVJWX-fCFo5RHrwfqvo3DqX1jP3=AFV4Bpw@mail.gmail.com> <mailman.487.1462671388.32212.python-list@python.org>

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On 5/7/2016 9:36 PM, Chris Angelico wrote:
> On Sun, May 8, 2016 at 11:16 AM, DFS <nospam@dfs.com> wrote:
>> On 5/7/2016 1:01 PM, Chris Angelico wrote:
>>> The suggestion from a human would be to use zip(), or possibly to
>>> change your data structures.
>>
>>
>> Happens like this:
>>
>> address data is scraped from a website:
>>
>> names = tree.xpath()
>> addr  = tree.xpath()
>>
>> I want to store the data atomically, so I parse street, city, state, and zip
>> into their own lists.
>>
>> "1250 Peachtree Rd, Atlanta, GA 30303
>>
>> street = [s.split(',')[0] for s in addr]
>> city   = [c.split(',')[1].strip() for c in addr]
>> state  = [s[-8:][:2] for s in addr]
>> zipcd  = [z[-5:] for z in addr]
>
> So you're iterating over addr lots of times, and building separate
> lists. As an alternative, you could iterate over it *once*, and have a
> single object representing an address.


I like the idea of one iteration, but how?   (I'll be trying myself 
before I check back in)

Remember, it's required to split the data up, to give flexibility in 
sorting, searching, output, etc.

I saw a cool example where someone built a list and used it to do a bulk 
INSERT.  That probably won't work well here, because one of the options 
I give the user is # of addresses to store.  So I do invididual INSERTs 
using the 'for j in range()' method, which makes it easier to track how 
many addresses have been stored.


>> Why is it better to zip() them up and use:
>>
>> for item1, item2, item3 in zip(list1, list2, list3):
>>      do something with the items
>>
>> than
>>
>>
>> for j in range(len(list1)):
>>    do something with list1[j], list2[j], list3[j], etc.
>
> Because 'j' is insignificant here, as is the length of the list.

Sorry, but I don't understand what you mean by insignificant.  j keeps 
track of the position in the list - regardless of the length of the list.


> What
> you're doing is iterating over three parallel lists - not counting
> numbers. Imagine that, instead of lists, you just have *sequences* -
> ordered collections of things. You can follow a recipe without knowing
> the numbers of the individual lines; you just need to know the
> sequence. Here, iterate over this collection:
>
> * Collect ingredients.
> * Cream the butter and the sugar.
> * Sift the salt into the flour.
> * Fold the mixture into an origami crane.
>
> These instructions work whether they're numbered or not.

Again, not following you.


The only reason

for j in range(len(list1)):
     do something with list1[j], list2[j], list3[j], etc.

or

for item1, item2, item3 in zip(list1, list2, list3):
     do something with the items

works is because each list has the same number of items.

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Thread

pylint woes DFS <nospam@dfs.com> - 2016-05-07 12:51 -0400
  Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 03:01 +1000
    Re: pylint woes DFS <nospam@dfs.com> - 2016-05-07 21:16 -0400
      Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 11:36 +1000
        Re: pylint woes DFS <nospam@dfs.com> - 2016-05-07 22:15 -0400
          Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 12:50 +1000
            Re: pylint woes DFS <nospam@dfs.com> - 2016-05-10 18:36 -0400
              Re: pylint woes MRAB <python@mrabarnett.plus.com> - 2016-05-11 02:02 +0100
      Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-07 19:14 -0700
        Re: pylint woes DFS <nospam@dfs.com> - 2016-05-07 23:04 -0400
          Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-07 20:46 -0700
            Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 10:26 -0400
          Re: pylint woes Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-05-08 08:50 +0300
            Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 10:25 -0400
              Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-09 00:36 +1000
                Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 11:06 -0400
                Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-08 08:15 -0700
                Re: pylint woes Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-05-09 13:17 +1200
                Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-09 12:18 +1000
                Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 22:58 -0400
                Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-09 01:15 +1000
                Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 17:06 -0400
              Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-08 08:11 -0700
              Re: pylint woes Steven D'Aprano <steve@pearwood.info> - 2016-05-09 01:51 +1000
                Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 17:04 -0400
                Re: pylint woes Steven D'Aprano <steve@pearwood.info> - 2016-05-09 13:09 +1000
      Re: pylint woes MRAB <python@mrabarnett.plus.com> - 2016-05-08 03:21 +0100
      Re: pylint woes Steven D'Aprano <steve@pearwood.info> - 2016-05-08 21:36 +1000
        Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 17:24 -0400
          Re: pylint woes Joel Goldstick <joel.goldstick@gmail.com> - 2016-05-08 17:39 -0400
          Re: pylint woes Steven D'Aprano <steve@pearwood.info> - 2016-05-09 13:46 +1000
  Re: pylint woes Michael Selik <michael.selik@gmail.com> - 2016-05-07 18:42 +0000
  Re: pylint woes Peter Pearson <pkpearson@nowhere.invalid> - 2016-05-07 18:43 +0000
    Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 17:05 -0400
  Re: pylint woes Christopher Reimer <christopher_reimer@icloud.com> - 2016-05-07 11:52 -0700
    Re: pylint woes DFS <nospam@dfs.com> - 2016-05-07 23:38 -0400
      Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 13:56 +1000
      Re: pylint woes Peter Otten <__peter__@web.de> - 2016-05-08 16:19 +0200
  Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-07 12:21 -0700
  Re: pylint woes Stephen Hansen <me@ixokai.io> - 2016-05-07 12:23 -0700
  Re: pylint woes Terry Reedy <tjreedy@udel.edu> - 2016-05-07 15:40 -0400
    Re: pylint woes DFS <nospam@dfs.com> - 2016-05-07 23:28 -0400
      Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 13:51 +1000
        Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 00:40 -0400
          Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 14:55 +1000
      Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-07 20:55 -0700
      Re: pylint woes Ian Kelly <ian.g.kelly@gmail.com> - 2016-05-07 23:09 -0600
      Re: pylint woes Peter Otten <__peter__@web.de> - 2016-05-08 16:12 +0200
  Re: pylint woes Christopher Reimer <christopher_reimer@icloud.com> - 2016-05-07 12:43 -0700
  Re: pylint woes Ray Cote <rgacote@appropriatesolutions.com> - 2016-05-07 15:52 -0400
  Re: pylint woes Christopher Reimer <christopher_reimer@icloud.com> - 2016-05-07 13:20 -0700
  Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 07:56 +1000
  Re: pylint woes Terry Reedy <tjreedy@udel.edu> - 2016-05-07 21:44 -0400
  Re: pylint woes Steven D'Aprano <steve@pearwood.info> - 2016-05-08 13:25 +1000
    Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 00:10 -0400
      Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 14:21 +1000
      Re: pylint woes "D'Arcy J.M. Cain" <darcy@VybeNetworks.com> - 2016-05-08 08:50 -0400
      Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-08 23:01 +1000
        Re: pylint woes Larry Hudson <orgnut@yahoo.com> - 2016-05-08 13:45 -0700
          Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-09 08:07 +1000
            Re: pylint woes Larry Hudson <orgnut@yahoo.com> - 2016-05-08 18:28 -0700
        Re: pylint woes Dan Sommers <dan@tombstonezero.net> - 2016-05-08 20:49 +0000
          Re: pylint woes Chris Angelico <rosuav@gmail.com> - 2016-05-09 08:10 +1000
      Re: pylint woes Steven D'Aprano <steve@pearwood.info> - 2016-05-09 03:25 +1000
        Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 17:16 -0400
          Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-08 14:38 -0700
            Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 17:46 -0400
              Re: pylint woes Stephen Hansen <me+python@ixokai.io> - 2016-05-08 15:05 -0700
                Re: pylint woes DFS <nospam@dfs.com> - 2016-05-08 18:24 -0400

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