Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: Ian Kelly <ian.g.kelly@gmail.com>
Newsgroups: comp.lang.python
Subject: Re: avoid for loop calling Generator function
Date: Mon, 22 Feb 2016 09:11:11 -0700
Lines: 41
Message-ID: <mailman.43.1456157520.20994.python-list@python.org>
References: <e5e4a934-4eeb-46ed-892f-cda9e903c1cd@googlegroups.com> <mailman.40.1456148110.20994.python-list@python.org> <0c289f93-ce64-4eff-93f3-c70d7ff50817@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8
In-Reply-To: <0c289f93-ce64-4eff-93f3-c70d7ff50817@googlegroups.com>
Precedence: list
Xref: csiph.com comp.lang.python:103346

On Mon, Feb 22, 2016 at 8:38 AM, Arshpreet Singh <arsh840@gmail.com> wrote:
> On Monday, 22 February 2016 19:05:24 UTC+5:30, Peter Otten  wrote:
>> or the slightly less convoluted
>>
>> sys.stdout.writelines(map("{}\n".format, read_pdf("book.pdf")))
>
> Actually I am using this function in Android App which is being built
using Kivy, Where I am returning whole text into a file, So what you think
will be more efficient way?

Profile them and find out, but I don't think you'll find the difference is
great enough to be overly concerned with. Pick the way that is more
readable and doesn't introduce any gross inefficiencies (such as
concatenating strings in a loop).

> But when I am calling pdf_read() from nother function to avoid for loop
why it is not working?
> say:
>
> def hello()
>     yield from read_pdf('book.pdf')

This uses yield from, which makes it a generator function.

>
> print(hello()) # still returns memory location instead of text. If I am
not wrong yield from can be used to avoid for loop?

hello is a generator function, so calling it just creates a generator
object. Printing it then prints out the repr of that generator object,
which is just something like <generator object hello at 0x7f6e82b124c0>.

Notably, you haven't actually *executed* the generator object, which would
require iterating over it, e.g.:

for i in hello():
    print(i)

So you haven't actually avoided creating a for loop; you've just added a
redundant layer between the for loop and the thing it's actually iterating
over.