<s>
Flask	B-Language
is	O
a	O
micro	O
web	B-Application
framework	I-Application
written	O
in	O
Python	B-Language
.	O
</s>
<s>
It	O
is	O
classified	O
as	O
a	O
microframework	B-Application
because	O
it	O
does	O
not	O
require	O
particular	O
tools	O
or	O
libraries	O
.	O
</s>
<s>
However	O
,	O
Flask	B-Language
supports	O
extensions	O
that	O
can	O
add	O
application	O
features	O
as	O
if	O
they	O
were	O
implemented	O
in	O
Flask	B-Language
itself	O
.	O
</s>
<s>
Applications	O
that	O
use	O
the	O
Flask	B-Language
framework	O
include	O
Pinterest	B-Application
and	O
LinkedIn	B-Application
.	O
</s>
<s>
Flask	B-Language
was	O
created	O
by	O
Armin	O
Ronacher	O
of	O
Pocoo	O
,	O
an	O
international	O
group	O
of	O
Python	B-Language
enthusiasts	O
formed	O
in	O
2004	O
.	O
</s>
<s>
When	O
Ronacher	O
and	O
Georg	O
Brandl	O
created	O
a	O
bulletin	O
board	O
system	O
written	O
in	O
Python	B-Language
in	O
2004	O
,	O
the	O
Pocoo	O
projects	O
Werkzeug	O
and	O
Jinja	B-Language
were	O
developed	O
.	O
</s>
<s>
In	O
April	O
2016	O
,	O
the	O
Pocoo	O
team	O
was	O
disbanded	O
and	O
development	O
of	O
Flask	B-Language
and	O
related	O
libraries	O
passed	O
to	O
the	O
newly	O
formed	O
Pallets	O
project	O
.	O
</s>
<s>
Since	O
2018	O
,	O
Flask-related	O
data	O
and	O
objects	O
can	O
be	O
rendered	O
with	O
Bootstrap	O
.	O
</s>
<s>
Flask	B-Language
has	O
become	O
popular	O
among	O
Python	B-Language
enthusiasts	O
.	O
</s>
<s>
,	O
it	O
has	O
second	O
most	O
stars	O
on	O
GitHub	B-Application
among	O
Python	B-Language
web-development	O
frameworks	O
,	O
only	O
slightly	O
behind	O
Django	B-Language
,	O
and	O
was	O
voted	O
the	O
most	O
popular	O
web	B-Application
framework	I-Application
in	O
the	O
Python	B-Language
Developers	O
Survey	O
2018	O
,	O
2019	O
,	O
2020	O
and	O
2021	O
.	O
</s>
<s>
The	O
microframework	B-Application
Flask	B-Language
is	O
part	O
of	O
the	O
Pallets	O
Projects	O
(	O
formerly	O
Pocoo	O
)	O
,	O
and	O
based	O
on	O
several	O
others	O
of	O
them	O
,	O
all	O
under	O
a	O
BSD	B-Operating_System
license	I-Operating_System
.	O
</s>
<s>
Werkzeug	O
(	O
German	O
for	O
"	O
tool	O
"	O
)	O
is	O
a	O
utility	O
library	O
for	O
the	O
Python	B-Language
programming	I-Language
language	I-Language
for	O
Web	B-Language
Server	I-Language
Gateway	I-Language
Interface	I-Language
(	O
WSGI	B-Language
)	O
applications	O
.	O
</s>
<s>
It	O
can	O
be	O
used	O
as	O
the	O
basis	O
for	O
a	O
custom	O
software	B-Architecture
framework	I-Architecture
and	O
supports	O
Python	B-Language
2.7	O
and	O
3.5	O
and	O
later	O
.	O
</s>
<s>
Jinja	B-Language
,	O
also	O
by	O
Ronacher	O
,	O
is	O
a	O
template	B-Application
engine	I-Application
for	O
the	O
Python	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
Similar	O
to	O
the	O
Django	B-Language
web	I-Language
framework	I-Language
,	O
it	O
handles	O
templates	O
in	O
a	O
sandbox	O
.	O
</s>
<s>
MarkupSafe	O
is	O
a	O
string	O
handling	O
library	O
for	O
the	O
Python	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
The	O
eponymous	O
MarkupSafe	O
type	O
extends	O
the	O
Python	B-Language
string	O
type	O
and	O
marks	O
its	O
contents	O
as	O
"	O
safe	O
"	O
;	O
combining	O
MarkupSafe	O
with	O
regular	O
strings	O
automatically	O
escapes	O
the	O
unmarked	O
strings	O
,	O
while	O
avoiding	O
double	O
escaping	O
of	O
already	O
marked	O
strings	O
.	O
</s>
<s>
ItsDangerous	O
is	O
a	O
safe	O
data	B-Application
serialization	I-Application
library	O
for	O
the	O
Python	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
It	O
is	O
used	O
to	O
store	O
the	O
session	B-Protocol
of	O
a	O
Flask	B-Language
application	O
in	O
a	O
cookie	B-Application
without	O
allowing	O
users	O
to	O
tamper	O
with	O
the	O
session	B-Protocol
contents	O
.	O
</s>
