<s>
CPython	B-Language
is	O
the	O
reference	O
implementation	O
of	O
the	O
Python	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
Written	O
in	O
C	B-Language
and	O
Python	B-Language
,	O
CPython	B-Language
is	O
the	O
default	O
and	O
most	O
widely	O
used	O
implementation	O
of	O
the	O
Python	B-Language
language	I-Language
.	O
</s>
<s>
CPython	B-Language
can	O
be	O
defined	O
as	O
both	O
an	O
interpreter	B-Application
and	O
a	O
compiler	B-Language
as	O
it	O
compiles	B-Language
Python	B-Language
code	I-Language
into	O
bytecode	O
before	O
interpreting	O
it	O
.	O
</s>
<s>
It	O
has	O
a	O
foreign	B-Application
function	I-Application
interface	I-Application
with	O
several	O
languages	O
,	O
including	O
C	B-Language
,	O
in	O
which	O
one	O
must	O
explicitly	O
write	O
bindings	B-Application
in	O
a	O
language	O
other	O
than	O
Python	B-Language
.	O
</s>
<s>
A	O
particular	O
feature	O
of	O
CPython	B-Language
is	O
that	O
it	O
makes	O
use	O
of	O
a	O
global	B-Operating_System
interpreter	I-Operating_System
lock	I-Operating_System
(	O
GIL	O
)	O
on	O
each	O
CPython	B-Language
interpreter	B-Application
process	B-Operating_System
,	O
which	O
means	O
that	O
within	O
a	O
single	O
process	B-Operating_System
,	O
only	O
one	O
thread	B-Operating_System
may	O
be	O
processing	O
Python	B-Language
bytecode	O
at	O
any	O
one	O
time	O
.	O
</s>
<s>
This	O
does	O
not	O
mean	O
that	O
there	O
is	O
no	O
point	O
in	O
multithreading	B-Operating_System
;	O
the	O
most	O
common	O
multithreading	B-Operating_System
scenario	O
is	O
where	O
threads	B-Operating_System
are	O
mostly	O
waiting	O
on	O
external	O
processes	O
to	O
complete	O
.	O
</s>
<s>
This	O
can	O
happen	O
when	O
multiple	O
threads	B-Operating_System
are	O
servicing	O
separate	O
clients	O
.	O
</s>
<s>
One	O
thread	B-Operating_System
may	O
be	O
waiting	O
for	O
a	O
client	O
to	O
reply	O
,	O
and	O
another	O
may	O
be	O
waiting	O
for	O
a	O
database	O
query	O
to	O
execute	O
,	O
while	O
the	O
third	O
thread	B-Operating_System
is	O
actually	O
processing	O
Python	B-Language
code	I-Language
.	O
</s>
<s>
However	O
,	O
the	O
GIL	O
does	O
mean	O
that	O
CPython	B-Language
is	O
not	O
suitable	O
for	O
processes	O
that	O
implement	O
CPU-intensive	O
algorithms	O
in	O
Python	B-Language
code	I-Language
that	O
could	O
potentially	O
be	O
distributed	O
across	O
multiple	O
cores	O
.	O
</s>
<s>
This	O
is	O
because	O
Python	B-Language
is	O
an	O
inherently	O
slow	O
language	O
and	O
is	O
generally	O
not	O
used	O
for	O
CPU-intensive	O
or	O
time-sensitive	O
operations	O
.	O
</s>
<s>
Python	B-Language
is	O
typically	O
used	O
at	O
the	O
top	O
level	O
and	O
calls	O
functions	O
in	O
libraries	O
to	O
perform	O
specialized	O
tasks	O
.	O
</s>
<s>
These	O
libraries	O
are	O
generally	O
not	O
written	O
in	O
Python	B-Language
,	O
and	O
Python	B-Language
code	I-Language
in	O
another	O
thread	B-Operating_System
can	O
be	O
executed	O
while	O
a	O
call	O
to	O
one	O
of	O
these	O
underlying	O
processes	O
takes	O
place	O
.	O
</s>
<s>
The	O
non-Python	O
library	O
being	O
called	O
to	O
perform	O
the	O
CPU-intensive	O
task	O
is	O
not	O
subject	O
to	O
the	O
GIL	O
and	O
may	O
concurrently	O
execute	O
many	O
threads	B-Operating_System
on	O
multiple	O
processors	O
without	O
restriction	O
.	O
</s>
<s>
Concurrency	O
of	O
Python	B-Language
code	I-Language
can	O
only	O
be	O
achieved	O
with	O
separate	O
CPython	B-Language
interpreter	B-Application
processes	O
managed	O
by	O
a	O
multitasking	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
.	O
</s>
<s>
This	O
complicates	O
communication	O
between	O
concurrent	B-Operating_System
Python	I-Operating_System
processes	I-Operating_System
,	O
though	O
the	O
multiprocessing	O
module	O
mitigates	O
this	O
somewhat	O
;	O
it	O
means	O
that	O
applications	O
that	O
really	O
can	O
benefit	O
from	O
concurrent	B-Operating_System
Python-code	O
execution	O
can	O
be	O
implemented	O
with	O
a	O
limited	O
amount	O
of	O
overhead	O
.	O
</s>
<s>
The	O
presence	O
of	O
the	O
GIL	O
simplifies	O
the	O
implementation	O
of	O
CPython	B-Language
,	O
and	O
makes	O
it	O
easier	O
to	O
implement	O
multi-threaded	B-Operating_System
applications	O
that	O
do	O
not	O
benefit	O
from	O
concurrent	B-Operating_System
Python	B-Language
code	I-Language
execution	O
.	O
</s>
<s>
However	O
,	O
without	O
a	O
GIL	O
,	O
multiprocessing	O
apps	O
must	O
make	O
sure	O
all	O
common	O
code	O
is	O
thread	B-Operating_System
safe	O
.	O
</s>
<s>
Unladen	O
Swallow	O
was	O
an	O
optimization	O
branch	O
of	O
CPython	B-Language
,	O
intended	O
to	O
be	O
fully	O
compatible	O
and	O
significantly	O
faster	O
.	O
</s>
<s>
It	O
aimed	O
to	O
achieve	O
its	O
goals	O
by	O
supplementing	O
CPython	B-Language
's	O
custom	O
virtual	B-Architecture
machine	I-Architecture
with	O
a	O
just-in-time	O
compiler	B-Language
built	O
using	O
LLVM	B-Application
.	O
</s>
<s>
The	O
project	O
had	O
stated	O
a	O
goal	O
of	O
a	O
speed	O
improvement	O
by	O
a	O
factor	O
of	O
five	O
over	O
CPython	B-Language
;	O
this	O
goal	O
was	O
not	O
met	O
.	O
</s>
<s>
The	O
project	O
was	O
sponsored	O
by	O
Google	B-Application
,	O
and	O
the	O
project	O
owners	O
,	O
Thomas	O
Wouters	O
,	O
Jeffrey	O
Yasskin	O
,	O
and	O
Collin	O
Winter	O
,	O
are	O
full-time	O
Google	B-Application
employees	O
;	O
however	O
,	O
most	O
project	O
contributors	O
were	O
not	O
Google	B-Application
employees	O
.	O
</s>
<s>
Unladen	O
Swallow	O
was	O
hosted	O
on	O
Google	B-Application
Code	I-Application
.	O
</s>
<s>
Like	O
many	O
things	O
regarding	O
the	O
Python	B-Language
language	I-Language
,	O
the	O
name	O
Unladen	O
Swallow	O
is	O
a	O
Monty	O
Python	B-Language
reference	O
,	O
specifically	O
to	O
the	O
joke	O
about	O
the	O
airspeed	O
velocity	O
of	O
unladen	O
swallows	O
in	O
Monty	O
Python	B-Language
and	O
the	O
Holy	O
Grail	O
.	O
</s>
<s>
Although	O
it	O
fell	O
short	O
of	O
all	O
published	O
goals	O
,	O
Unladen	O
Swallow	O
did	O
produce	O
some	O
code	O
that	O
got	O
added	O
to	O
the	O
main	O
Python	B-Language
implementation	O
,	O
such	O
as	O
improvements	O
to	O
the	O
cPickle	O
module	O
.	O
</s>
<s>
It	O
has	O
also	O
been	O
reported	O
that	O
Unladen	O
lost	O
Google	B-Application
's	I-Application
funding	O
.	O
</s>
<s>
In	O
November	O
2010	O
,	O
one	O
of	O
the	O
main	O
developers	O
announced	O
that	O
"	O
Jeffrey	O
and	O
I	O
have	O
been	O
pulled	O
on	O
to	O
other	O
projects	O
of	O
higher	O
importance	O
to	O
Google	B-Application
"	O
.	O
</s>
<s>
Further	O
,	O
regarding	O
the	O
long-term	O
plans	O
,	O
and	O
as	O
the	O
project	O
missed	O
the	O
Python	B-Language
2.7	O
release	O
,	O
a	O
Python	B-Language
Enhancement	O
Proposal	O
(	O
PEP	O
)	O
was	O
accepted	O
,	O
which	O
proposed	O
a	O
merge	O
of	O
Unladen	O
Swallow	O
into	O
a	O
special	O
py3k-jit	O
branch	O
of	O
Python	B-Language
's	O
official	O
repository	B-General_Concept
.	O
</s>
<s>
This	O
merging	O
would	O
have	O
taken	O
some	O
time	O
,	O
since	O
Unladen	O
Swallow	O
was	O
originally	O
based	O
on	O
Python	B-Language
2.6	O
with	O
which	O
Python	B-Language
3	O
broke	O
compatibility	O
(	O
see	O
Python	B-Language
3000	O
for	O
more	O
details	O
)	O
.	O
</s>
<s>
Officially	O
supported	O
tier-1	O
platforms	O
are	O
Windows	O
,	O
Linux	B-Application
and	O
macOS	B-Application
(	O
and	O
also	O
Raspberry	B-Application
Pi	I-Application
OS	I-Application
,	O
and	O
Linux	B-Application
for	O
s390x	O
on	O
lower	O
tier	O
)	O
.	O
</s>
<s>
PEP	O
11	O
lists	O
platforms	O
which	O
are	O
not	O
supported	O
in	O
CPython	B-Language
by	O
the	O
Python	B-Application
Software	I-Application
Foundation	I-Application
.	O
</s>
<s>
External	O
ports	O
not	O
integrated	O
to	O
Python	B-Application
Software	I-Application
Foundation	I-Application
's	O
official	O
version	O
of	O
CPython	B-Language
,	O
with	O
links	O
to	O
its	O
main	O
development	O
site	O
,	O
often	O
include	O
additional	O
modules	O
for	O
platform-specific	O
functionalities	O
,	O
like	O
graphics	O
and	O
sound	O
API	O
for	O
PSP	B-Operating_System
and	O
SMS	O
and	O
camera	O
API	O
for	O
S60	B-Language
.	O
</s>
<s>
These	O
Python	B-Language
versions	O
are	O
distributed	O
with	O
currently-supported	O
enterprise	O
Linux	B-Application
distributions	O
.	O
</s>
<s>
The	O
support	O
status	O
of	O
Python	B-Language
in	O
the	O
table	O
refers	O
to	O
support	O
from	O
the	O
Python	B-Language
core	O
team	O
,	O
and	O
not	O
from	O
the	O
distribution	O
maintainer	O
.	O
</s>
<s>
CPython	B-Language
is	O
one	O
of	O
several	O
"	O
production-quality	O
"	O
Python	B-Language
implementations	O
including	O
:	O
Jython	B-Language
,	O
written	O
in	O
Java	B-Language
for	O
the	O
Java	B-Language
virtual	I-Language
machine	I-Language
(	O
JVM	B-Language
)	O
,	O
PyPy	B-Language
,	O
written	O
in	O
RPython	B-Language
and	O
translated	O
into	O
C	B-Language
,	O
and	O
IronPython	B-Application
,	O
which	O
is	O
written	O
in	O
C#	B-Application
for	O
the	O
Common	O
Language	O
Infrastructure	O
.	O
</s>
