Path: csiph.com!news.mixmin.net!weretis.net!feeder1.news.weretis.net!news.roellig-ltd.de!open-news-network.org!border2.nntp.ams1.giganews.com!nntp.giganews.com!usenetcore.com!newsfeed.xs4all.nl!newsfeed7.news.xs4all.nl!nzpost1.xs4all.net!not-for-mail
To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: continue vs. pass in this IO reading and writing
Date: Thu, 3 Sep 2015 12:05:28 -0400
References: <19ca6361-95fe-4a5d-84d6-c72d7941745c@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0
In-Reply-To: <19ca6361-95fe-4a5d-84d6-c72d7941745c@googlegroups.com>
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.79.1441296357.8327.python-list@python.org>
Lines: 60
NNTP-Posting-Host: 2001:888:2000:d::a6
Xref: csiph.com comp.lang.python:95952

On 9/3/2015 11:05 AM, kbtyo wrote:

> I am experimenting with many exception handling and utilizing continue vs pass.

'pass' is a do-nothing place holder.  'continue' and 'break' are jump 
statements

[snip]

> However, I am uncertain as to how this executes in a context like this:
>
> import glob
> import csv
> from collections import OrderedDict
>
> interesting_files = glob.glob("*.csv")
>
> header_saved = False
> with open('merged_output_mod.csv','w') as fout:
>
>      for filename in interesting_files:
>          print("execution here again")
>          with open(filename) as fin:
>              try:
>                  header = next(fin)
>                  print("Entering Try and Except")
>              except:
>                  StopIteration
>                  continue
>              else:
>                  if not header_saved:
>                      fout.write(header)
>                      header_saved = True
>                      print("We got here")
>                  for line in fin:
>                      fout.write(line)
>
> My questions are (for some reason my interpreter does not print out any readout):
>
> 1. after the exception is raised does the continue return back up to the beginning of the for loop (and the "else" conditional is not even encountered)?
>
> 2. How would a pass behave in this situation?

Try it for yourself.  Copy the following into a python shell or editor 
(and run) see what you get.

for i in [-1, 0, 1]:
     try:
         j = 2//i
     except ZeroDivisionError:
         print('infinity')
         continue
     else:
         print(j)

Change 'continue' to 'pass' and run again.

-- 
Terry Jan Reedy