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Date: Mon, 29 Oct 2012 11:08:10 -0400
Subject: Re: I need help installing pypng in Python 3.3
From: David Robinow <drobinow@gmail.com>
To: icgwh@tagyourself.com
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On Mon, Oct 29, 2012 at 8:23 AM,  <icgwh@tagyourself.com> wrote:
> Hello all,
>
> I am very new to python. I am currently porting a little project of mine =
from java to python and I need to be able to construct and write png images=
. I naturally turned myself toward pypng to accomplish this.
>
> I learned from the net that pypng 0.0.13 is supposed to work in Python 3.=
x when run through '2to3'. However, in my case, it apparently does not.
>
You haven't shown that.
> I ran into various problems when trying to install it, some of them I cou=
ld fix myself. First I attempted to install pip but I couldn't get Windows =
to recognize pip as an internal command as the prompt informs me.
 No, it's not an internal command, but you don't need that. I'm
assuming your python is installed under C:\Python33. If not, adjust as
needed.  Try:
 C:\Python33\Scripts\pip install pypng

[You didn't say what you did to install pip so I don't know if pip.exe
actually exists in C:\Python33\Scripts]

> Then I tried to directly run "setup.py install" from the pypng folder. It=
 didn't work as I got a syntax error. I noticed that in the beginning of th=
e installation process, the following warning was displayed: "conf[use_2to3=
 =3D true] unrecognized configuration option"

 The following works for me:
C:\Python33\python setup.py install

>
> At that point I was already pretty pissed but I managed to make the warni=
ng disappear by updating (installing?) distribute. After that there are no =
more errors during the installation process and everything seems to work fi=
ne. (This seems still strange to me as 2to3 was present in Tools/Script out=
 of the box)

It's not clear what you did here. setup.py should run 2to3 for you.
What command did you use to successfully? install it?

> I use pydev in Eclipse and pydev reports several error in png.py anytime =
I want to import or use it. When trying to import from IDLE I get:
>
> except ValueError, e:
>                  ^
> Syntax error, line 1863
 It's clear that the install process didn't run 2to3.

> that paricular error I was able to fix by changing it to "except ValueErr=
or as e:" but I don't understand why 2to3 didn't do it automatically.
 2to3 does do it automatically.
> There are several more errors reported by pydev, here are a few:
>
> line 1368 : "raise ValueError('Chunk %s too short for checksum.', tag)"
>             Undefined variable: tag

Looking at the code, this appears to be a bug.
>
> line 2736 : "rows =3D [map(numpy.uint16, range(0,0x10000,0x5555))]"
>             Undefined variable from import: uint16
>
> The second one made me suspect I needed to install numpy too. As there ar=
e no installers for numpy aimed toward Python3.3.
 A few lines above there's a try/except for importing numpy. It should
skip this test if numpy is not available. I'm not sure how you were
able to execute that line [unless you've got a stray numpy.py  file
somewhere somewhere]

> I decided to install Python2.7 and retry the whole process. Unfortunately=
 I didn't get much more success. I get the exact same errors in pydev when =
using the 2.7 version of the interpreter and I cannot install numpy either =
because when I run the .exe file aimed toward Python 2.7 i get the error me=
ssage:
>
> "Python version 2.7 required, which was not found in the registry"
>
> I then have the option to manually enter the path to Python 2.7 but the t=
extform is greyed out and I can't type in anything.
>

Do you have the file c:\Python33\Lib\site-packages\pypng-0.0.13-py3.3.egg  =
?
If not, you have not successfully installed pypng. Please try one of
the methods I gave above.