Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!xlned.com!feeder1.xlned.com!newsfeed.xs4all.nl!newsfeed2.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
MIME-Version: 1.0
Sender: joshua.landau.ws@gmail.com
In-Reply-To: <b16bb894-a720-4e0c-a3ce-d699afffeb8e@googlegroups.com>
References: <c6702eb3-494a-4359-84ef-d6679c09df35@googlegroups.com> <dfa6368b-565b-4512-8755-ef36fd2719cd@googlegroups.com> <b16bb894-a720-4e0c-a3ce-d699afffeb8e@googlegroups.com>
From: Joshua Landau <joshua@landau.ws>
Date: Sat, 3 Aug 2013 03:11:37 +0100
Subject: Re: Python: Code is ignoring the if and else
To: kevin4fong@gmail.com
Content-Type: multipart/alternative; boundary=001a11c37e0cc9be2804e3019a34
Cc: python-list <python-list@python.org>
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.142.1375495945.1251.python-list@python.org>
Lines: 86
NNTP-Posting-Host: 2001:888:2000:d::a6
Xref: csiph.com comp.lang.python:51839

--001a11c37e0cc9be2804e3019a34
Content-Type: text/plain; charset=UTF-8

On 3 August 2013 02:44, <kevin4fong@gmail.com> wrote:

> Yeah, I already know about that. But if I try to change it, I'm not even
> able to start the program. If I try to change the if statement that it
> corresponds with, I get a an error saying "card" is not a global. And if I
> try to shift it in, for some reason...the program runs through the MISS
> line multiple times.
>

You have a car with a broken engine and a broken tire and are telling us
that you refuse to fix the engine because it highlights the problem of the
broken tire.

Take the fix and move on to the next problem.

One piece of advice is about scoping. This is perhaps the hardest "gotcha"
of Python conceptually, but it's sensible once you understand the
justifications.

Run the four commands below and try and understand why this applies to your
code.

a = 1

def access_global():
    print(a)

def set_variable():
    a = 2
    print(a)

def broken_set():
    a = a + 1
    print(a)

def also_broken():
    print(a)
    return
    a = 1 # Never run!

The fix for the broken variants is to start the functions with "global a".

--001a11c37e0cc9be2804e3019a34
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr">On 3 August 2013 02:44,  <span dir=3D"ltr">&lt;<a href=3D"=
mailto:kevin4fong@gmail.com" target=3D"_blank">kevin4fong@gmail.com</a>&gt;=
</span> wrote:<div class=3D"gmail_extra"><div class=3D"gmail_quote"><blockq=
uote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc =
solid;padding-left:1ex">

Yeah, I already know about that. But if I try to change it, I&#39;m not eve=
n able to start the program. If I try to change the if statement that it co=
rresponds with, I get a an error saying &quot;card&quot; is not a global. A=
nd if I try to shift it in, for some reason...the program runs through the =
MISS line multiple times.<br>

</blockquote><div><br></div><div>You have a car with a broken engine and a =
broken tire and are telling us that you refuse to fix the engine because it=
 highlights the problem of the broken tire.</div><div><br></div><div>Take t=
he fix and move on to the next problem.</div>

<div><br></div><div>One piece of advice is about scoping. This is perhaps t=
he hardest &quot;gotcha&quot; of Python conceptually, but it&#39;s sensible=
 once you understand the justifications.</div><div><br></div><div>Run the f=
our commands below and try and understand why this applies to your code.</d=
iv>

<div><br></div><div>a =3D 1</div><div><br></div><div>def access_global():</=
div><div>=C2=A0 =C2=A0 print(a)</div><div><br></div><div>def set_variable()=
:</div><div>=C2=A0 =C2=A0 a =3D 2</div><div>=C2=A0 =C2=A0 print(a)</div><di=
v><br></div><div>def broken_set():</div>

<div>=C2=A0 =C2=A0 a =3D a + 1</div><div>=C2=A0 =C2=A0 print(a)</div><div><=
br></div><div>def also_broken():</div><div>=C2=A0 =C2=A0 print(a)</div><div=
>=C2=A0 =C2=A0 return</div><div>=C2=A0 =C2=A0 a =3D 1 # Never run!</div><di=
v><br></div><div>The fix for the broken variants is to start the functions =
with &quot;global a&quot;.</div>

<div><br></div></div></div></div>

--001a11c37e0cc9be2804e3019a34--