<s>
Python	B-Language
Paste	I-Language
,	O
often	O
simply	O
called	O
paste	O
,	O
is	O
a	O
set	O
of	O
utilities	B-Application
for	O
web	O
development	O
in	O
Python	B-Language
.	O
</s>
<s>
Paste	O
has	O
been	O
described	O
as	O
"	O
a	O
framework	O
for	O
web	B-Application
frameworks	I-Application
"	O
.	O
</s>
<s>
The	O
Python	B-Language
Paste	I-Language
package	O
contains	O
Python	B-Language
modules	O
that	O
help	O
in	O
implementing	O
WSGI	B-Language
middleware	O
.	O
</s>
<s>
The	O
package	O
includes	O
a	O
WSGI	B-Language
wrapper	O
for	O
CGI	B-Language
applications	O
.	O
</s>
<s>
It	O
also	O
includes	O
a	O
simple	O
webserver	B-Application
that	O
can	O
produce	O
WSGI	B-Language
requests	O
.	O
</s>
<s>
The	O
WSGI	B-Language
standard	O
is	O
an	O
interface	O
that	O
allows	O
applications	O
to	O
use	O
Python	B-Language
code	I-Language
to	O
handle	O
HTTP	O
requests	O
.	O
</s>
<s>
A	O
WSGI	B-Language
application	O
is	O
passed	O
a	O
Python	B-Language
representation	O
of	O
an	O
HTTP	O
request	O
by	O
an	O
application	O
,	O
and	O
returns	O
content	O
which	O
will	O
normally	O
eventually	O
be	O
rendered	O
by	O
a	O
web	O
browser	O
.	O
</s>
<s>
A	O
common	O
use	O
for	O
this	O
is	O
when	O
a	O
web	B-Application
server	I-Application
serves	O
content	O
created	O
by	O
Python	B-Language
code	I-Language
.	O
</s>
<s>
There	O
are	O
,	O
however	O
,	O
other	O
uses	O
:	O
WSGI	B-Language
middleware	O
is	O
Python	B-Language
code	I-Language
that	O
receives	O
a	O
WSGI	B-Language
request	O
and	O
then	O
performs	O
logic	O
based	O
upon	O
this	O
request	O
,	O
before	O
passing	O
the	O
request	O
on	O
to	O
a	O
WSGI	B-Language
application	O
or	O
more	O
WSGI	B-Language
middleware	O
.	O
</s>
<s>
WSGI	B-Language
middleware	O
appears	O
to	O
an	O
application	O
as	O
a	O
server	O
,	O
and	O
to	O
the	O
server	O
as	O
an	O
application	O
.	O
</s>
<s>
This	O
is	O
analogous	O
to	O
the	O
function	O
of	O
pipes	B-Operating_System
on	I-Operating_System
Unix	I-Operating_System
systems	I-Operating_System
.	O
</s>
<s>
Functionality	O
provided	O
by	O
WSGI	B-Language
middleware	O
may	O
include	O
authentication	O
,	O
logging	O
,	O
URL	O
redirection	O
,	O
creation	O
of	O
sessions	O
,	O
and	O
compression	O
.	O
</s>
<s>
Paste	O
helps	O
in	O
developing	O
such	O
WSGI	B-Language
middleware	O
systems	O
.	O
</s>
<s>
For	O
example	O
,	O
it	O
is	O
used	O
in	O
the	O
Pylons	B-Language
web	B-Application
application	I-Application
framework	I-Application
.	O
</s>
<s>
As	O
it	O
has	O
grown	O
,	O
it	O
has	O
unbundled	O
several	O
other	O
utilities	B-Application
from	O
the	O
Paste	O
core	O
.	O
</s>
<s>
These	O
utilities	B-Application
are	O
part	O
of	O
the	O
Paste	O
project	O
,	O
but	O
form	O
their	O
own	O
packages	O
and	O
have	O
their	O
own	O
version	O
numbers	O
.	O
</s>
<s>
Paste	O
Deploy	O
is	O
a	O
system	O
for	O
finding	O
and	O
configuring	O
WSGI	B-Language
applications	O
and	O
servers	O
.	O
</s>
<s>
WebOb	O
is	O
a	O
wrapper	O
around	O
the	O
WSGI	B-Language
environment	O
.	O
</s>
<s>
WebTest	O
and	O
WebOb	O
have	O
migrated	O
and	O
are	O
now	O
part	O
of	O
the	O
Pylons	B-Operating_System
project	I-Operating_System
.	O
</s>
